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	$85.52	12.148%	$95.909	$95.91	$95.90	$95.90
Purchase #2	$60.54	11.532%	$67.5215	$67.52	$67.50	$67.50
Purchase #3	$120.69	7.825%	$130.134	$130.13	$130.15	$130.10
Purchase #4	$145.36	10.573%	$160.7289	$160.73	$160.75	$160.70
Purchase #5	$250.33	13.649%	$284.4975	$284.50	$284.50	$284.50
Purchase #6	$241.56	13.352%	$273.8131	$273.81	$273.80	$273.80
Purchase #7	$196.47	11.280%	$218.6318	$218.63	$218.65	$218.60
7 purchase totals =	$1,100.47		$1,231.2358	$1,231.23	$1,231.25	$1,231.10