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	$72.46	7.224%	$77.6945	$77.69	$77.70	$77.70
Purchase #2	$202.85	3.295%	$209.5339	$209.53	$209.55	$209.50
Purchase #3	$59.34	3.370%	$61.3398	$61.34	$61.35	$61.30
Purchase #4	$165.61	3.815%	$171.928	$171.93	$171.95	$171.90
Purchase #5	$72.39	13.840%	$82.4088	$82.41	$82.40	$82.40
Purchase #6	$87.33	4.467%	$91.231	$91.23	$91.25	$91.20
Purchase #7	$230.55	10.329%	$254.3635	$254.36	$254.35	$254.40
7 purchase totals =	$890.53		$948.4995	$948.49	$948.55	$948.40