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	$59.29	3.247%	$61.2151	$61.22	$61.20	$61.20
Purchase #2	$7.51	4.287%	$7.832	$7.83	$7.85	$7.80
Purchase #3	$133.55	4.519%	$139.5851	$139.59	$139.60	$139.60
Purchase #4	$135.35	11.204%	$150.5146	$150.51	$150.50	$150.50
Purchase #5	$244.55	13.802%	$278.3028	$278.30	$278.30	$278.30
Purchase #6	$71.43	11.293%	$79.4966	$79.50	$79.50	$79.50
Purchase #7	$15.54	6.645%	$16.5726	$16.57	$16.55	$16.60
7 purchase totals =	$667.22		$733.5188	$733.52	$733.50	$733.50