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	$160.25	8.239%	$173.453	$173.45	$173.45	$173.50
Purchase #2	$243.48	8.333%	$263.7692	$263.77	$263.75	$263.80
Purchase #3	$157.72	6.406%	$167.8235	$167.82	$167.80	$167.80
Purchase #4	$130.89	10.241%	$144.2944	$144.29	$144.30	$144.30
Purchase #5	$51.26	7.520%	$55.1148	$55.11	$55.10	$55.10
Purchase #6	$143.99	11.731%	$160.8815	$160.88	$160.90	$160.90
Purchase #7	$178.32	7.249%	$191.2464	$191.25	$191.25	$191.20
7 purchase totals =	$1,065.91		$1,156.5828	$1,156.57	$1,156.55	$1,156.60