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	$168.53	13.664%	$191.5579	$191.56	$191.55	$191.60
Purchase #2	$184.34	3.738%	$191.2306	$191.23	$191.25	$191.20
Purchase #3	$212.29	6.324%	$225.7152	$225.72	$225.70	$225.70
Purchase #4	$152.88	6.407%	$162.675	$162.68	$162.70	$162.70
Purchase #5	$233.72	8.846%	$254.3949	$254.39	$254.40	$254.40
Purchase #6	$72.82	13.642%	$82.7541	$82.75	$82.75	$82.80
Purchase #7	$24.39	11.302%	$27.1466	$27.15	$27.15	$27.10
7 purchase totals =	$1,048.97		$1,135.4743	$1,135.48	$1,135.50	$1,135.50