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	$124.27	9.356%	$135.8967	$135.90	$135.90	$135.90
Purchase #2	$146.32	3.121%	$150.8866	$150.89	$150.90	$150.90
Purchase #3	$56.41	4.169%	$58.7617	$58.76	$58.75	$58.80
Purchase #4	$82.77	3.570%	$85.7249	$85.72	$85.70	$85.70
Purchase #5	$85.43	11.494%	$95.2493	$95.25	$95.25	$95.20
Purchase #6	$150.79	3.644%	$156.2848	$156.28	$156.30	$156.30
Purchase #7	$29.57	9.683%	$32.4333	$32.43	$32.45	$32.40
7 purchase totals =	$675.56		$715.2373	$715.23	$715.25	$715.20