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	$186.73	12.298%	$209.6941	$209.69	$209.70	$209.70
Purchase #2	$137.28	11.273%	$152.7556	$152.76	$152.75	$152.80
Purchase #3	$181.39	11.306%	$201.898	$201.90	$201.90	$201.90
Purchase #4	$60.60	11.122%	$67.3399	$67.34	$67.35	$67.30
Purchase #5	$181.86	8.222%	$196.8125	$196.81	$196.80	$196.80
Purchase #6	$240.97	3.298%	$248.9172	$248.92	$248.90	$248.90
Purchase #7	$167.83	8.215%	$181.6172	$181.62	$181.60	$181.60
7 purchase totals =	$1,156.66		$1,259.0345	$1,259.04	$1,259.00	$1,259.00