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	$53.69	8.441%	$58.222	$58.22	$58.20	$58.20
Purchase #2	$112.96	6.725%	$120.5566	$120.56	$120.55	$120.60
Purchase #3	$41.58	3.647%	$43.0964	$43.10	$43.10	$43.10
Purchase #4	$54.51	3.182%	$56.2445	$56.24	$56.25	$56.20
Purchase #5	$72.46	3.584%	$75.057	$75.06	$75.05	$75.10
Purchase #6	$144.70	12.307%	$162.5082	$162.51	$162.50	$162.50
Purchase #7	$83.93	7.503%	$90.2273	$90.23	$90.25	$90.20
7 purchase totals =	$563.83		$605.9120	$605.92	$605.90	$605.90