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	$117.91	12.364%	$132.4884	$132.49	$132.50	$132.50
Purchase #2	$58.61	12.124%	$65.7159	$65.72	$65.70	$65.70
Purchase #3	$212.47	13.698%	$241.5741	$241.57	$241.55	$241.60
Purchase #4	$73.40	7.328%	$78.7788	$78.78	$78.80	$78.80
Purchase #5	$249.98	6.437%	$266.0712	$266.07	$266.05	$266.10
Purchase #6	$90.77	10.506%	$100.3063	$100.31	$100.30	$100.30
Purchase #7	$233.42	4.704%	$244.4001	$244.40	$244.40	$244.40
7 purchase totals =	$1,036.56		$1,129.3348	$1,129.34	$1,129.30	$1,129.40