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	$202.97	8.192%	$219.5973	$219.60	$219.60	$219.60
Purchase #2	$25.30	13.202%	$28.6401	$28.64	$28.65	$28.60
Purchase #3	$146.31	8.614%	$158.9131	$158.91	$158.90	$158.90
Purchase #4	$174.56	11.137%	$194.0007	$194.00	$194.00	$194.00
Purchase #5	$242.47	5.406%	$255.5779	$255.58	$255.60	$255.60
Purchase #6	$199.89	6.344%	$212.571	$212.57	$212.55	$212.60
Purchase #7	$27.61	12.114%	$30.9547	$30.95	$30.95	$31.00
7 purchase totals =	$1,019.11		$1,100.2548	$1,100.25	$1,100.25	$1,100.30