Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$236.53	13.497%	$268.4545	$268.45	$268.45	$268.50
Purchase #2	$94.30	7.819%	$101.6733	$101.67	$101.65	$101.70
Purchase #3	$166.65	7.811%	$179.667	$179.67	$179.65	$179.70
Purchase #4	$143.45	10.479%	$158.4821	$158.48	$158.50	$158.50
Purchase #5	$208.84	11.596%	$233.0571	$233.06	$233.05	$233.10
Purchase #6	$131.85	7.188%	$141.3274	$141.33	$141.35	$141.30
Purchase #7	$164.29	13.718%	$186.8273	$186.83	$186.85	$186.80
7 purchase totals =	$1,145.91		$1,269.4887	$1,269.49	$1,269.50	$1,269.60