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	$44.53	9.722%	$48.8592	$48.86	$48.85	$48.90
Purchase #2	$211.91	3.429%	$219.1764	$219.18	$219.20	$219.20
Purchase #3	$150.85	9.531%	$165.2275	$165.23	$165.25	$165.20
Purchase #4	$44.30	3.571%	$45.882	$45.88	$45.90	$45.90
Purchase #5	$114.64	11.165%	$127.4396	$127.44	$127.45	$127.40
Purchase #6	$189.48	11.160%	$210.626	$210.63	$210.65	$210.60
Purchase #7	$85.92	5.212%	$90.3982	$90.40	$90.40	$90.40
7 purchase totals =	$841.63		$907.6089	$907.62	$907.70	$907.60