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	$70.57	3.369%	$72.9475	$72.95	$72.95	$72.90
Purchase #2	$28.90	6.149%	$30.6771	$30.68	$30.70	$30.70
Purchase #3	$61.53	10.251%	$67.8374	$67.84	$67.85	$67.80
Purchase #4	$36.53	9.511%	$40.0044	$40.00	$40.00	$40.00
Purchase #5	$202.73	9.475%	$221.9387	$221.94	$221.95	$221.90
Purchase #6	$45.30	9.272%	$49.5002	$49.50	$49.50	$49.50
Purchase #7	$82.82	11.236%	$92.1257	$92.13	$92.15	$92.10
7 purchase totals =	$528.38		$575.0310	$575.04	$575.10	$574.90