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	$119.77	6.239%	$127.2425	$127.24	$127.25	$127.20
Purchase #2	$41.39	4.560%	$43.2774	$43.28	$43.30	$43.30
Purchase #3	$100.76	10.245%	$111.0829	$111.08	$111.10	$111.10
Purchase #4	$181.27	6.318%	$192.7226	$192.72	$192.70	$192.70
Purchase #5	$23.81	8.850%	$25.9172	$25.92	$25.90	$25.90
Purchase #6	$244.71	12.475%	$275.2376	$275.24	$275.25	$275.20
Purchase #7	$90.71	9.678%	$99.4889	$99.49	$99.50	$99.50
7 purchase totals =	$802.42		$874.9691	$874.97	$875.00	$874.90