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	$144.45	4.692%	$151.2276	$151.23	$151.25	$151.20
Purchase #2	$118.82	7.640%	$127.8978	$127.90	$127.90	$127.90
Purchase #3	$106.40	13.583%	$120.8523	$120.85	$120.85	$120.90
Purchase #4	$42.92	9.816%	$47.133	$47.13	$47.15	$47.10
Purchase #5	$62.81	4.549%	$65.6672	$65.67	$65.65	$65.70
Purchase #6	$40.53	11.457%	$45.1735	$45.17	$45.15	$45.20
Purchase #7	$244.25	8.443%	$264.872	$264.87	$264.85	$264.90
7 purchase totals =	$760.18		$822.8234	$822.82	$822.80	$822.90