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	$198.94	5.827%	$210.5322	$210.53	$210.55	$210.50
Purchase #2	$179.37	13.532%	$203.6423	$203.64	$203.65	$203.60
Purchase #3	$45.72	8.755%	$49.7228	$49.72	$49.70	$49.70
Purchase #4	$53.32	11.459%	$59.4299	$59.43	$59.45	$59.40
Purchase #5	$63.40	3.220%	$65.4415	$65.44	$65.45	$65.40
Purchase #6	$230.78	4.796%	$241.8482	$241.85	$241.85	$241.80
Purchase #7	$65.86	11.665%	$73.5426	$73.54	$73.55	$73.50
7 purchase totals =	$837.39		$904.1595	$904.15	$904.20	$903.90