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	$78.47	8.657%	$85.2631	$85.26	$85.25	$85.30
Purchase #2	$89.48	4.739%	$93.7205	$93.72	$93.70	$93.70
Purchase #3	$137.63	9.814%	$151.137	$151.14	$151.15	$151.10
Purchase #4	$168.42	4.329%	$175.7109	$175.71	$175.70	$175.70
Purchase #5	$211.76	12.651%	$238.5498	$238.55	$238.55	$238.50
Purchase #6	$90.77	7.181%	$97.2882	$97.29	$97.30	$97.30
Purchase #7	$190.61	13.604%	$216.5406	$216.54	$216.55	$216.50
7 purchase totals =	$967.14		$1,058.2101	$1,058.21	$1,058.20	$1,058.10