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	$59.82	4.796%	$62.689	$62.69	$62.70	$62.70
Purchase #2	$240.61	6.612%	$256.5191	$256.52	$256.50	$256.50
Purchase #3	$106.90	5.739%	$113.035	$113.04	$113.05	$113.00
Purchase #4	$157.76	13.450%	$178.9787	$178.98	$179.00	$179.00
Purchase #5	$106.50	11.115%	$118.3375	$118.34	$118.35	$118.30
Purchase #6	$36.59	3.486%	$37.8655	$37.87	$37.85	$37.90
Purchase #7	$23.39	8.600%	$25.4015	$25.40	$25.40	$25.40
7 purchase totals =	$731.57		$792.8263	$792.84	$792.85	$792.80