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	$55.62	12.282%	$62.4512	$62.45	$62.45	$62.50
Purchase #2	$168.70	13.485%	$191.4492	$191.45	$191.45	$191.40
Purchase #3	$241.48	11.114%	$268.3181	$268.32	$268.30	$268.30
Purchase #4	$131.83	7.849%	$142.1773	$142.18	$142.20	$142.20
Purchase #5	$122.58	6.787%	$130.8995	$130.90	$130.90	$130.90
Purchase #6	$106.72	12.283%	$119.8284	$119.83	$119.85	$119.80
Purchase #7	$134.86	8.206%	$145.9266	$145.93	$145.95	$145.90
7 purchase totals =	$961.79		$1,061.0503	$1,061.06	$1,061.10	$1,061.00