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	$188.48	4.277%	$196.5413	$196.54	$196.55	$196.50
Purchase #2	$148.45	3.525%	$153.6829	$153.68	$153.70	$153.70
Purchase #3	$134.77	11.865%	$150.7605	$150.76	$150.75	$150.80
Purchase #4	$243.67	8.457%	$264.2772	$264.28	$264.30	$264.30
Purchase #5	$50.37	6.747%	$53.7685	$53.77	$53.75	$53.80
Purchase #6	$235.82	10.207%	$259.8901	$259.89	$259.90	$259.90
Purchase #7	$229.47	5.645%	$242.4236	$242.42	$242.40	$242.40
7 purchase totals =	$1,231.03		$1,321.3441	$1,321.34	$1,321.35	$1,321.40