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	$223.51	7.731%	$240.7896	$240.79	$240.80	$240.80
Purchase #2	$117.39	8.643%	$127.536	$127.54	$127.55	$127.50
Purchase #3	$75.45	9.413%	$82.5521	$82.55	$82.55	$82.60
Purchase #4	$88.59	7.600%	$95.3228	$95.32	$95.30	$95.30
Purchase #5	$100.64	8.760%	$109.4561	$109.46	$109.45	$109.50
Purchase #6	$222.29	11.496%	$247.8445	$247.84	$247.85	$247.80
Purchase #7	$118.47	7.689%	$127.5792	$127.58	$127.60	$127.60
7 purchase totals =	$946.34		$1,031.0803	$1,031.08	$1,031.10	$1,031.10