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	$247.99	5.671%	$262.0535	$262.05	$262.05	$262.10
Purchase #2	$124.49	5.700%	$131.5859	$131.59	$131.60	$131.60
Purchase #3	$193.33	4.576%	$202.1768	$202.18	$202.20	$202.20
Purchase #4	$229.37	11.281%	$255.2452	$255.25	$255.25	$255.20
Purchase #5	$41.84	3.508%	$43.3077	$43.31	$43.30	$43.30
Purchase #6	$178.59	3.685%	$185.171	$185.17	$185.15	$185.20
Purchase #7	$151.56	13.451%	$171.9463	$171.95	$171.95	$171.90
7 purchase totals =	$1,167.17		$1,251.4864	$1,251.50	$1,251.50	$1,251.50