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	$75.54	8.576%	$82.0183	$82.02	$82.00	$82.00
Purchase #2	$32.63	13.708%	$37.1029	$37.10	$37.10	$37.10
Purchase #3	$136.38	7.700%	$146.8813	$146.88	$146.90	$146.90
Purchase #4	$230.76	11.736%	$257.842	$257.84	$257.85	$257.80
Purchase #5	$7.65	3.341%	$7.9056	$7.91	$7.90	$7.90
Purchase #6	$236.82	12.384%	$266.1478	$266.15	$266.15	$266.10
Purchase #7	$204.61	7.361%	$219.6713	$219.67	$219.65	$219.70
7 purchase totals =	$924.39		$1,017.5692	$1,017.57	$1,017.55	$1,017.50