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	$147.78	3.554%	$153.0321	$153.03	$153.05	$153.00
Purchase #2	$235.47	8.822%	$256.2432	$256.24	$256.25	$256.20
Purchase #3	$129.66	3.119%	$133.7041	$133.70	$133.70	$133.70
Purchase #4	$41.52	6.632%	$44.2736	$44.27	$44.25	$44.30
Purchase #5	$238.35	9.749%	$261.5867	$261.59	$261.60	$261.60
Purchase #6	$115.56	13.581%	$131.2542	$131.25	$131.25	$131.30
Purchase #7	$157.67	9.348%	$172.409	$172.41	$172.40	$172.40
7 purchase totals =	$1,066.01		$1,152.5029	$1,152.49	$1,152.50	$1,152.50