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	$145.82	5.221%	$153.4333	$153.43	$153.45	$153.40
Purchase #2	$77.44	5.121%	$81.4057	$81.41	$81.40	$81.40
Purchase #3	$75.33	13.629%	$85.5967	$85.60	$85.60	$85.60
Purchase #4	$191.51	12.661%	$215.7571	$215.76	$215.75	$215.80
Purchase #5	$36.63	7.207%	$39.2699	$39.27	$39.25	$39.30
Purchase #6	$55.90	7.584%	$60.1395	$60.14	$60.15	$60.10
Purchase #7	$28.66	12.778%	$32.3222	$32.32	$32.30	$32.30
7 purchase totals =	$611.29		$667.9244	$667.93	$667.90	$667.90