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	$212.54	8.792%	$231.2265	$231.23	$231.25	$231.20
Purchase #2	$93.51	3.206%	$96.5079	$96.51	$96.50	$96.50
Purchase #3	$59.70	9.441%	$65.3363	$65.34	$65.35	$65.30
Purchase #4	$51.48	5.479%	$54.3006	$54.30	$54.30	$54.30
Purchase #5	$220.31	11.374%	$245.3681	$245.37	$245.35	$245.40
Purchase #6	$170.76	5.340%	$179.8786	$179.88	$179.90	$179.90
Purchase #7	$125.34	3.863%	$130.1819	$130.18	$130.20	$130.20
7 purchase totals =	$933.64		$1,002.7999	$1,002.81	$1,002.85	$1,002.80