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	$33.52	10.429%	$37.0158	$37.02	$37.00	$37.00
Purchase #2	$235.96	13.317%	$267.3828	$267.38	$267.40	$267.40
Purchase #3	$65.54	10.815%	$72.6282	$72.63	$72.65	$72.60
Purchase #4	$96.33	10.175%	$106.1316	$106.13	$106.15	$106.10
Purchase #5	$86.50	5.403%	$91.1736	$91.17	$91.15	$91.20
Purchase #6	$94.74	5.409%	$99.8645	$99.86	$99.85	$99.90
Purchase #7	$10.88	9.716%	$11.9371	$11.94	$11.95	$11.90
7 purchase totals =	$623.47		$686.1336	$686.13	$686.15	$686.10