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	$143.71	9.129%	$156.8293	$156.83	$156.85	$156.80
Purchase #2	$242.33	5.168%	$254.8536	$254.85	$254.85	$254.90
Purchase #3	$53.77	10.359%	$59.34	$59.34	$59.35	$59.30
Purchase #4	$233.73	7.552%	$251.3813	$251.38	$251.40	$251.40
Purchase #5	$50.47	11.461%	$56.2544	$56.25	$56.25	$56.30
Purchase #6	$159.41	12.596%	$179.4893	$179.49	$179.50	$179.50
Purchase #7	$211.85	9.623%	$232.2363	$232.24	$232.25	$232.20
7 purchase totals =	$1,095.27		$1,190.3842	$1,190.38	$1,190.45	$1,190.40