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	$232.82	3.821%	$241.7161	$241.72	$241.70	$241.70
Purchase #2	$203.35	3.292%	$210.0443	$210.04	$210.05	$210.00
Purchase #3	$209.37	6.661%	$223.3161	$223.32	$223.30	$223.30
Purchase #4	$74.50	10.725%	$82.4901	$82.49	$82.50	$82.50
Purchase #5	$68.57	4.854%	$71.8984	$71.90	$71.90	$71.90
Purchase #6	$88.89	5.480%	$93.7612	$93.76	$93.75	$93.80
Purchase #7	$147.26	6.114%	$156.2635	$156.26	$156.25	$156.30
7 purchase totals =	$1,024.76		$1,079.4897	$1,079.49	$1,079.45	$1,079.50