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	$229.62	3.357%	$237.3283	$237.33	$237.35	$237.30
Purchase #2	$191.43	10.281%	$211.1109	$211.11	$211.10	$211.10
Purchase #3	$49.28	8.269%	$53.355	$53.36	$53.35	$53.40
Purchase #4	$90.79	5.196%	$95.5074	$95.51	$95.50	$95.50
Purchase #5	$173.86	7.735%	$187.3081	$187.31	$187.30	$187.30
Purchase #6	$82.28	4.820%	$86.2459	$86.25	$86.25	$86.20
Purchase #7	$82.92	9.109%	$90.4732	$90.47	$90.45	$90.50
7 purchase totals =	$900.18		$961.3288	$961.34	$961.30	$961.30