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	$209.62	9.358%	$229.2362	$229.24	$229.25	$229.20
Purchase #2	$23.68	4.670%	$24.7859	$24.79	$24.80	$24.80
Purchase #3	$26.36	13.516%	$29.9228	$29.92	$29.90	$29.90
Purchase #4	$38.91	12.121%	$43.6263	$43.63	$43.65	$43.60
Purchase #5	$33.44	12.168%	$37.509	$37.51	$37.50	$37.50
Purchase #6	$38.57	6.139%	$40.9378	$40.94	$40.95	$40.90
Purchase #7	$39.97	13.835%	$45.4998	$45.50	$45.50	$45.50
7 purchase totals =	$410.55		$451.5178	$451.53	$451.55	$451.40