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	$191.67	10.453%	$211.7053	$211.71	$211.70	$211.70
Purchase #2	$77.59	6.290%	$82.4704	$82.47	$82.45	$82.50
Purchase #3	$204.76	7.551%	$220.2214	$220.22	$220.20	$220.20
Purchase #4	$93.97	6.306%	$99.8957	$99.90	$99.90	$99.90
Purchase #5	$53.78	10.635%	$59.4995	$59.50	$59.50	$59.50
Purchase #6	$132.97	7.498%	$142.9401	$142.94	$142.95	$142.90
Purchase #7	$88.88	7.668%	$95.6953	$95.70	$95.70	$95.70
7 purchase totals =	$843.62		$912.4277	$912.44	$912.40	$912.40