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	$167.51	10.778%	$185.5642	$185.56	$185.55	$185.60
Purchase #2	$82.63	6.275%	$87.815	$87.82	$87.80	$87.80
Purchase #3	$250.32	11.655%	$279.4948	$279.49	$279.50	$279.50
Purchase #4	$75.76	8.309%	$82.0549	$82.05	$82.05	$82.10
Purchase #5	$147.79	4.450%	$154.3667	$154.37	$154.35	$154.40
Purchase #6	$137.98	3.743%	$143.1446	$143.14	$143.15	$143.10
Purchase #7	$194.39	12.576%	$218.8365	$218.84	$218.85	$218.80
7 purchase totals =	$1,056.38		$1,151.2767	$1,151.27	$1,151.25	$1,151.30