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	$200.96	10.865%	$222.7943	$222.79	$222.80	$222.80
Purchase #2	$10.80	9.191%	$11.7926	$11.79	$11.80	$11.80
Purchase #3	$188.77	7.836%	$203.562	$203.56	$203.55	$203.60
Purchase #4	$48.55	9.103%	$52.9695	$52.97	$52.95	$53.00
Purchase #5	$30.94	8.328%	$33.5167	$33.52	$33.50	$33.50
Purchase #6	$130.31	10.824%	$144.4148	$144.41	$144.40	$144.40
Purchase #7	$28.99	7.526%	$31.1718	$31.17	$31.15	$31.20
7 purchase totals =	$639.32		$700.2217	$700.21	$700.15	$700.30