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	$196.90	13.334%	$223.1546	$223.15	$223.15	$223.20
Purchase #2	$18.94	11.106%	$21.0435	$21.04	$21.05	$21.00
Purchase #3	$138.36	11.152%	$153.7899	$153.79	$153.80	$153.80
Purchase #4	$230.67	13.502%	$261.8151	$261.82	$261.80	$261.80
Purchase #5	$35.83	5.298%	$37.7283	$37.73	$37.75	$37.70
Purchase #6	$196.28	11.873%	$219.5843	$219.58	$219.60	$219.60
Purchase #7	$130.90	4.211%	$136.4122	$136.41	$136.40	$136.40
7 purchase totals =	$947.88		$1,053.5279	$1,053.52	$1,053.55	$1,053.50