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	$228.85	9.585%	$250.7853	$250.79	$250.80	$250.80
Purchase #2	$71.86	4.247%	$74.9119	$74.91	$74.90	$74.90
Purchase #3	$149.55	6.404%	$159.1272	$159.13	$159.15	$159.10
Purchase #4	$218.36	13.221%	$247.2294	$247.23	$247.25	$247.20
Purchase #5	$86.67	6.623%	$92.4102	$92.41	$92.40	$92.40
Purchase #6	$159.82	4.733%	$167.3843	$167.38	$167.40	$167.40
Purchase #7	$144.89	3.781%	$150.3683	$150.37	$150.35	$150.40
7 purchase totals =	$1,060.00		$1,142.2166	$1,142.22	$1,142.25	$1,142.20