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	$118.79	12.422%	$133.5461	$133.55	$133.55	$133.50
Purchase #2	$170.59	8.617%	$185.2897	$185.29	$185.30	$185.30
Purchase #3	$200.48	13.592%	$227.7292	$227.73	$227.75	$227.70
Purchase #4	$39.85	3.245%	$41.1431	$41.14	$41.15	$41.10
Purchase #5	$89.39	11.609%	$99.7673	$99.77	$99.75	$99.80
Purchase #6	$203.98	6.818%	$217.8874	$217.89	$217.90	$217.90
Purchase #7	$235.58	12.696%	$265.4892	$265.49	$265.50	$265.50
7 purchase totals =	$1,058.66		$1,170.8520	$1,170.86	$1,170.90	$1,170.80