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	$96.53	10.155%	$106.3326	$106.33	$106.35	$106.30
Purchase #2	$51.29	12.209%	$57.552	$57.55	$57.55	$57.60
Purchase #3	$150.53	5.561%	$158.901	$158.90	$158.90	$158.90
Purchase #4	$145.55	12.796%	$164.1746	$164.17	$164.15	$164.20
Purchase #5	$72.91	7.786%	$78.5868	$78.59	$78.60	$78.60
Purchase #6	$97.70	4.290%	$101.8913	$101.89	$101.90	$101.90
Purchase #7	$117.54	7.277%	$126.0934	$126.09	$126.10	$126.10
7 purchase totals =	$732.05		$793.5317	$793.52	$793.55	$793.60