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	$245.97	3.468%	$254.5002	$254.50	$254.50	$254.50
Purchase #2	$220.82	7.353%	$237.0569	$237.06	$237.05	$237.10
Purchase #3	$75.32	9.198%	$82.2479	$82.25	$82.25	$82.20
Purchase #4	$26.93	7.338%	$28.9061	$28.91	$28.90	$28.90
Purchase #5	$78.65	5.285%	$82.8067	$82.81	$82.80	$82.80
Purchase #6	$227.82	6.519%	$242.6716	$242.67	$242.65	$242.70
Purchase #7	$198.80	11.642%	$221.9443	$221.94	$221.95	$221.90
7 purchase totals =	$1,074.31		$1,150.1337	$1,150.14	$1,150.10	$1,150.10