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	$188.92	4.181%	$196.8187	$196.82	$196.80	$196.80
Purchase #2	$218.44	13.660%	$248.2789	$248.28	$248.30	$248.30
Purchase #3	$234.97	13.726%	$267.222	$267.22	$267.20	$267.20
Purchase #4	$17.37	3.325%	$17.9476	$17.95	$17.95	$17.90
Purchase #5	$99.55	6.693%	$106.2129	$106.21	$106.20	$106.20
Purchase #6	$89.37	10.685%	$98.9192	$98.92	$98.90	$98.90
Purchase #7	$86.59	11.472%	$96.5236	$96.52	$96.50	$96.50
7 purchase totals =	$935.21		$1,031.9229	$1,031.92	$1,031.85	$1,031.80