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	$224.36	8.842%	$244.1979	$244.20	$244.20	$244.20
Purchase #2	$145.55	6.648%	$155.2262	$155.23	$155.25	$155.20
Purchase #3	$59.29	4.369%	$61.8804	$61.88	$61.90	$61.90
Purchase #4	$66.62	7.115%	$71.36	$71.36	$71.35	$71.40
Purchase #5	$236.91	11.707%	$264.6451	$264.65	$264.65	$264.60
Purchase #6	$49.88	6.407%	$53.0758	$53.08	$53.10	$53.10
Purchase #7	$219.71	11.683%	$245.3787	$245.38	$245.40	$245.40
7 purchase totals =	$1,002.32		$1,095.7641	$1,095.78	$1,095.85	$1,095.80