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	$171.28	13.683%	$194.7162	$194.72	$194.70	$194.70
Purchase #2	$120.39	9.134%	$131.3864	$131.39	$131.40	$131.40
Purchase #3	$147.96	8.219%	$160.1208	$160.12	$160.10	$160.10
Purchase #4	$137.85	7.756%	$148.5416	$148.54	$148.55	$148.50
Purchase #5	$189.43	13.764%	$215.5031	$215.50	$215.50	$215.50
Purchase #6	$154.41	6.479%	$164.4142	$164.41	$164.40	$164.40
Purchase #7	$156.83	13.561%	$178.0977	$178.10	$178.10	$178.10
7 purchase totals =	$1,078.15		$1,192.7800	$1,192.78	$1,192.75	$1,192.70