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	$197.83	12.331%	$222.2244	$222.22	$222.20	$222.20
Purchase #2	$194.72	11.813%	$217.7223	$217.72	$217.70	$217.70
Purchase #3	$224.90	8.440%	$243.8816	$243.88	$243.90	$243.90
Purchase #4	$165.91	3.475%	$171.6754	$171.68	$171.70	$171.70
Purchase #5	$195.79	9.201%	$213.8046	$213.80	$213.80	$213.80
Purchase #6	$219.32	11.427%	$244.3817	$244.38	$244.40	$244.40
Purchase #7	$65.86	8.722%	$71.6043	$71.60	$71.60	$71.60
7 purchase totals =	$1,264.33		$1,385.2943	$1,385.28	$1,385.30	$1,385.30