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	$113.74	8.495%	$123.4022	$123.40	$123.40	$123.40
Purchase #2	$9.46	13.472%	$10.7345	$10.73	$10.75	$10.70
Purchase #3	$243.53	13.310%	$275.9438	$275.94	$275.95	$275.90
Purchase #4	$75.49	12.647%	$85.0372	$85.04	$85.05	$85.00
Purchase #5	$215.76	4.250%	$224.9298	$224.93	$224.95	$224.90
Purchase #6	$208.92	6.755%	$223.0325	$223.03	$223.05	$223.00
Purchase #7	$105.56	6.800%	$112.7381	$112.74	$112.75	$112.70
7 purchase totals =	$972.46		$1,055.8181	$1,055.81	$1,055.90	$1,055.60