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	$53.70	8.244%	$58.127	$58.13	$58.15	$58.10
Purchase #2	$49.90	3.655%	$51.7238	$51.72	$51.70	$51.70
Purchase #3	$222.43	5.681%	$235.0662	$235.07	$235.05	$235.10
Purchase #4	$31.31	6.588%	$33.3727	$33.37	$33.35	$33.40
Purchase #5	$229.41	11.478%	$255.7417	$255.74	$255.75	$255.70
Purchase #6	$223.30	13.506%	$253.4589	$253.46	$253.45	$253.50
Purchase #7	$225.51	4.559%	$235.791	$235.79	$235.80	$235.80
7 purchase totals =	$1,035.56		$1,123.2813	$1,123.28	$1,123.25	$1,123.30