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	$97.78	4.278%	$101.963	$101.96	$101.95	$102.00
Purchase #2	$131.88	10.485%	$145.7076	$145.71	$145.70	$145.70
Purchase #3	$69.36	10.379%	$76.5589	$76.56	$76.55	$76.60
Purchase #4	$42.64	7.654%	$45.9037	$45.90	$45.90	$45.90
Purchase #5	$221.40	13.122%	$250.4521	$250.45	$250.45	$250.50
Purchase #6	$128.26	10.194%	$141.3348	$141.33	$141.35	$141.30
Purchase #7	$180.31	8.649%	$195.905	$195.91	$195.90	$195.90
7 purchase totals =	$871.63		$957.8251	$957.82	$957.80	$957.90