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	$56.38	10.201%	$62.1313	$62.13	$62.15	$62.10
Purchase #2	$65.59	4.414%	$68.4851	$68.49	$68.50	$68.50
Purchase #3	$214.44	4.105%	$223.2428	$223.24	$223.25	$223.20
Purchase #4	$46.84	3.601%	$48.5267	$48.53	$48.55	$48.50
Purchase #5	$42.70	7.269%	$45.8039	$45.80	$45.80	$45.80
Purchase #6	$55.50	6.864%	$59.3095	$59.31	$59.30	$59.30
Purchase #7	$129.97	7.832%	$140.1493	$140.15	$140.15	$140.10
7 purchase totals =	$611.42		$647.6486	$647.65	$647.70	$647.50