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	$175.79	8.283%	$190.3507	$190.35	$190.35	$190.40
Purchase #2	$59.97	4.455%	$62.6417	$62.64	$62.65	$62.60
Purchase #3	$181.56	12.377%	$204.0317	$204.03	$204.05	$204.00
Purchase #4	$206.91	5.478%	$218.2445	$218.24	$218.25	$218.20
Purchase #5	$98.74	3.116%	$101.8167	$101.82	$101.80	$101.80
Purchase #6	$92.41	7.707%	$99.532	$99.53	$99.55	$99.50
Purchase #7	$84.34	6.653%	$89.9511	$89.95	$89.95	$90.00
7 purchase totals =	$899.72		$966.5684	$966.56	$966.60	$966.50