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	$250.50	3.624%	$259.5781	$259.58	$259.60	$259.60
Purchase #2	$38.78	5.160%	$40.781	$40.78	$40.80	$40.80
Purchase #3	$179.27	7.424%	$192.579	$192.58	$192.60	$192.60
Purchase #4	$188.26	6.639%	$200.7586	$200.76	$200.75	$200.80
Purchase #5	$234.36	5.731%	$247.7912	$247.79	$247.80	$247.80
Purchase #6	$32.46	4.326%	$33.8642	$33.86	$33.85	$33.90
Purchase #7	$69.30	3.258%	$71.5578	$71.56	$71.55	$71.60
7 purchase totals =	$992.93		$1,046.9099	$1,046.91	$1,046.95	$1,047.10