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	$212.73	12.270%	$238.832	$238.83	$238.85	$238.80
Purchase #2	$247.54	3.838%	$257.0406	$257.04	$257.05	$257.00
Purchase #3	$77.81	5.611%	$82.1759	$82.18	$82.20	$82.20
Purchase #4	$59.31	4.281%	$61.8491	$61.85	$61.85	$61.80
Purchase #5	$203.76	13.193%	$230.6421	$230.64	$230.65	$230.60
Purchase #6	$125.95	6.295%	$133.8786	$133.88	$133.90	$133.90
Purchase #7	$98.54	11.343%	$109.7174	$109.72	$109.70	$109.70
7 purchase totals =	$1,025.64		$1,114.1357	$1,114.14	$1,114.20	$1,114.00