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	$175.90	10.545%	$194.4487	$194.45	$194.45	$194.40
Purchase #2	$209.86	6.323%	$223.1294	$223.13	$223.15	$223.10
Purchase #3	$47.76	4.765%	$50.0358	$50.04	$50.05	$50.00
Purchase #4	$208.56	3.433%	$215.7199	$215.72	$215.70	$215.70
Purchase #5	$125.54	13.594%	$142.6059	$142.61	$142.60	$142.60
Purchase #6	$65.78	8.794%	$71.5647	$71.56	$71.55	$71.60
Purchase #7	$169.25	13.874%	$192.7317	$192.73	$192.75	$192.70
7 purchase totals =	$1,002.65		$1,090.2361	$1,090.24	$1,090.25	$1,090.10