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	$131.50	13.122%	$148.7554	$148.76	$148.75	$148.80
Purchase #2	$58.88	5.692%	$62.2314	$62.23	$62.25	$62.20
Purchase #3	$154.90	10.699%	$171.4728	$171.47	$171.45	$171.50
Purchase #4	$18.28	12.118%	$20.4952	$20.50	$20.50	$20.50
Purchase #5	$90.87	11.270%	$101.111	$101.11	$101.10	$101.10
Purchase #6	$141.40	6.327%	$150.3464	$150.35	$150.35	$150.30
Purchase #7	$179.61	7.103%	$192.3677	$192.37	$192.35	$192.40
7 purchase totals =	$775.44		$846.7799	$846.79	$846.75	$846.80