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	$166.40	10.633%	$184.0933	$184.09	$184.10	$184.10
Purchase #2	$149.70	12.353%	$168.1924	$168.19	$168.20	$168.20
Purchase #3	$77.84	7.862%	$83.9598	$83.96	$83.95	$84.00
Purchase #4	$100.42	11.410%	$111.8779	$111.88	$111.90	$111.90
Purchase #5	$137.30	7.530%	$147.6387	$147.64	$147.65	$147.60
Purchase #6	$144.44	7.812%	$155.7237	$155.72	$155.70	$155.70
Purchase #7	$202.87	3.596%	$210.1652	$210.17	$210.15	$210.20
7 purchase totals =	$978.97		$1,061.6510	$1,061.65	$1,061.65	$1,061.70