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	$108.97	3.480%	$112.7622	$112.76	$112.75	$112.80
Purchase #2	$249.96	12.830%	$282.0299	$282.03	$282.05	$282.00
Purchase #3	$45.53	13.740%	$51.7858	$51.79	$51.80	$51.80
Purchase #4	$205.93	8.343%	$223.1107	$223.11	$223.10	$223.10
Purchase #5	$40.54	13.116%	$45.8572	$45.86	$45.85	$45.90
Purchase #6	$185.56	10.870%	$205.7304	$205.73	$205.75	$205.70
Purchase #7	$135.94	4.254%	$141.7229	$141.72	$141.70	$141.70
7 purchase totals =	$972.43		$1,062.9991	$1,063.00	$1,063.00	$1,063.00