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	$183.72	5.538%	$193.8944	$193.89	$193.90	$193.90
Purchase #2	$141.29	9.727%	$155.0333	$155.03	$155.05	$155.00
Purchase #3	$58.39	5.290%	$61.4788	$61.48	$61.50	$61.50
Purchase #4	$210.91	4.811%	$221.0569	$221.06	$221.05	$221.10
Purchase #5	$38.85	5.735%	$41.078	$41.08	$41.10	$41.10
Purchase #6	$69.97	4.234%	$72.9325	$72.93	$72.95	$72.90
Purchase #7	$62.69	6.130%	$66.5329	$66.53	$66.55	$66.50
7 purchase totals =	$765.82		$812.0068	$812.00	$812.10	$812.00