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	$87.27	4.440%	$91.1448	$91.14	$91.15	$91.10
Purchase #2	$55.83	6.289%	$59.3411	$59.34	$59.35	$59.30
Purchase #3	$82.46	8.130%	$89.164	$89.16	$89.15	$89.20
Purchase #4	$84.34	12.286%	$94.702	$94.70	$94.70	$94.70
Purchase #5	$177.43	4.236%	$184.9459	$184.95	$184.95	$184.90
Purchase #6	$89.71	4.519%	$93.764	$93.76	$93.75	$93.80
Purchase #7	$75.55	9.674%	$82.8587	$82.86	$82.85	$82.90
7 purchase totals =	$652.59		$695.9205	$695.91	$695.90	$695.90