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	$59.75	4.775%	$62.6031	$62.60	$62.60	$62.60
Purchase #2	$101.71	5.800%	$107.6092	$107.61	$107.60	$107.60
Purchase #3	$85.51	11.561%	$95.3958	$95.40	$95.40	$95.40
Purchase #4	$188.33	8.700%	$204.7147	$204.71	$204.70	$204.70
Purchase #5	$85.27	4.352%	$88.981	$88.98	$89.00	$89.00
Purchase #6	$34.35	11.651%	$38.3521	$38.35	$38.35	$38.40
Purchase #7	$181.59	5.641%	$191.8335	$191.83	$191.85	$191.80
7 purchase totals =	$736.51		$789.4894	$789.48	$789.50	$789.50