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	$223.51	13.251%	$253.1273	$253.13	$253.15	$253.10
Purchase #2	$127.97	6.696%	$136.5389	$136.54	$136.55	$136.50
Purchase #3	$149.42	10.243%	$164.7251	$164.73	$164.75	$164.70
Purchase #4	$37.97	6.802%	$40.5527	$40.55	$40.55	$40.60
Purchase #5	$178.33	6.873%	$190.5866	$190.59	$190.60	$190.60
Purchase #6	$44.61	10.716%	$49.3904	$49.39	$49.40	$49.40
Purchase #7	$187.73	13.132%	$212.3827	$212.38	$212.40	$212.40
7 purchase totals =	$949.54		$1,047.3037	$1,047.31	$1,047.40	$1,047.30