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	$29.34	12.385%	$32.9738	$32.97	$32.95	$33.00
Purchase #2	$189.86	3.237%	$196.0058	$196.01	$196.00	$196.00
Purchase #3	$42.32	10.534%	$46.778	$46.78	$46.80	$46.80
Purchase #4	$121.74	8.159%	$131.6728	$131.67	$131.65	$131.70
Purchase #5	$52.67	3.842%	$54.6936	$54.69	$54.70	$54.70
Purchase #6	$203.69	12.229%	$228.5993	$228.60	$228.60	$228.60
Purchase #7	$96.39	8.323%	$104.4125	$104.41	$104.40	$104.40
7 purchase totals =	$736.01		$795.1358	$795.13	$795.10	$795.20