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	$98.35	5.241%	$103.5045	$103.50	$103.50	$103.50
Purchase #2	$130.45	11.839%	$145.894	$145.89	$145.90	$145.90
Purchase #3	$155.49	5.790%	$164.4929	$164.49	$164.50	$164.50
Purchase #4	$188.59	11.370%	$210.0327	$210.03	$210.05	$210.00
Purchase #5	$31.68	12.825%	$35.743	$35.74	$35.75	$35.70
Purchase #6	$104.77	3.131%	$108.0503	$108.05	$108.05	$108.10
Purchase #7	$110.26	6.579%	$117.514	$117.51	$117.50	$117.50
7 purchase totals =	$819.59		$885.2314	$885.21	$885.25	$885.20