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	$155.33	8.128%	$167.9552	$167.96	$167.95	$168.00
Purchase #2	$211.86	3.553%	$219.3874	$219.39	$219.40	$219.40
Purchase #3	$227.48	5.741%	$240.5396	$240.54	$240.55	$240.50
Purchase #4	$228.97	11.634%	$255.6084	$255.61	$255.60	$255.60
Purchase #5	$130.90	4.171%	$136.3598	$136.36	$136.35	$136.40
Purchase #6	$79.44	12.845%	$89.6441	$89.64	$89.65	$89.60
Purchase #7	$227.86	8.419%	$247.0435	$247.04	$247.05	$247.00
7 purchase totals =	$1,261.84		$1,356.5380	$1,356.54	$1,356.55	$1,356.50