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	$241.92	11.570%	$269.9101	$269.91	$269.90	$269.90
Purchase #2	$212.59	10.811%	$235.5731	$235.57	$235.55	$235.60
Purchase #3	$199.64	10.452%	$220.5064	$220.51	$220.50	$220.50
Purchase #4	$37.67	7.823%	$40.6169	$40.62	$40.60	$40.60
Purchase #5	$78.83	13.380%	$89.3775	$89.38	$89.40	$89.40
Purchase #6	$199.36	6.324%	$211.9675	$211.97	$211.95	$212.00
Purchase #7	$110.51	7.331%	$118.6115	$118.61	$118.60	$118.60
7 purchase totals =	$1,080.52		$1,186.5630	$1,186.57	$1,186.50	$1,186.60