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	$95.94	6.821%	$102.4841	$102.48	$102.50	$102.50
Purchase #2	$190.30	3.494%	$196.9491	$196.95	$196.95	$196.90
Purchase #3	$32.50	12.216%	$36.4702	$36.47	$36.45	$36.50
Purchase #4	$172.94	12.517%	$194.5869	$194.59	$194.60	$194.60
Purchase #5	$210.59	7.686%	$226.7759	$226.78	$226.80	$226.80
Purchase #6	$160.60	12.804%	$181.1632	$181.16	$181.15	$181.20
Purchase #7	$72.51	5.783%	$76.7033	$76.70	$76.70	$76.70
7 purchase totals =	$935.38		$1,015.1327	$1,015.13	$1,015.15	$1,015.20