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	$33.79	5.141%	$35.5271	$35.53	$35.55	$35.50
Purchase #2	$129.76	9.644%	$142.2741	$142.27	$142.25	$142.30
Purchase #3	$250.51	6.132%	$265.8713	$265.87	$265.85	$265.90
Purchase #4	$55.78	10.377%	$61.5683	$61.57	$61.55	$61.60
Purchase #5	$171.83	13.459%	$194.9566	$194.96	$194.95	$195.00
Purchase #6	$100.78	7.607%	$108.4463	$108.45	$108.45	$108.40
Purchase #7	$177.69	11.141%	$197.4864	$197.49	$197.50	$197.50
7 purchase totals =	$920.14		$1,006.1301	$1,006.14	$1,006.10	$1,006.20