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	$53.40	7.556%	$57.4349	$57.43	$57.45	$57.40
Purchase #2	$247.39	7.238%	$265.2961	$265.30	$265.30	$265.30
Purchase #3	$33.60	8.512%	$36.46	$36.46	$36.45	$36.50
Purchase #4	$123.83	4.304%	$129.1596	$129.16	$129.15	$129.20
Purchase #5	$154.90	6.285%	$164.6355	$164.64	$164.65	$164.60
Purchase #6	$159.90	12.213%	$179.4286	$179.43	$179.45	$179.40
Purchase #7	$227.91	12.627%	$256.6882	$256.69	$256.70	$256.70
7 purchase totals =	$1,000.93		$1,089.1029	$1,089.11	$1,089.15	$1,089.10