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	$151.43	11.412%	$168.7112	$168.71	$168.70	$168.70
Purchase #2	$120.44	6.251%	$127.9687	$127.97	$127.95	$128.00
Purchase #3	$77.77	8.614%	$84.4691	$84.47	$84.45	$84.50
Purchase #4	$28.56	12.723%	$32.1937	$32.19	$32.20	$32.20
Purchase #5	$54.31	11.491%	$60.5508	$60.55	$60.55	$60.60
Purchase #6	$67.61	7.623%	$72.7639	$72.76	$72.75	$72.80
Purchase #7	$137.74	9.838%	$151.2909	$151.29	$151.30	$151.30
7 purchase totals =	$637.86		$697.9483	$697.94	$697.90	$698.10