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	$223.38	3.498%	$231.1938	$231.19	$231.20	$231.20
Purchase #2	$240.75	13.369%	$272.9359	$272.94	$272.95	$272.90
Purchase #3	$79.77	7.360%	$85.6411	$85.64	$85.65	$85.60
Purchase #4	$193.65	3.694%	$200.8034	$200.80	$200.80	$200.80
Purchase #5	$177.86	10.388%	$196.3361	$196.34	$196.35	$196.30
Purchase #6	$32.61	5.653%	$34.4534	$34.45	$34.45	$34.50
Purchase #7	$98.44	3.581%	$101.9651	$101.97	$101.95	$102.00
7 purchase totals =	$1,046.46		$1,123.3288	$1,123.33	$1,123.35	$1,123.30