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	$43.76	9.293%	$47.8266	$47.83	$47.85	$47.80
Purchase #2	$153.76	7.643%	$165.5119	$165.51	$165.50	$165.50
Purchase #3	$115.98	7.415%	$124.5799	$124.58	$124.60	$124.60
Purchase #4	$89.51	5.587%	$94.5109	$94.51	$94.50	$94.50
Purchase #5	$145.37	4.206%	$151.4843	$151.48	$151.50	$151.50
Purchase #6	$147.35	12.411%	$165.6376	$165.64	$165.65	$165.60
Purchase #7	$35.63	9.751%	$39.1043	$39.10	$39.10	$39.10
7 purchase totals =	$731.36		$788.6555	$788.65	$788.70	$788.60