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	$233.98	13.381%	$265.2889	$265.29	$265.30	$265.30
Purchase #2	$245.50	9.400%	$268.577	$268.58	$268.60	$268.60
Purchase #3	$246.27	3.513%	$254.9215	$254.92	$254.90	$254.90
Purchase #4	$54.93	7.850%	$59.242	$59.24	$59.25	$59.20
Purchase #5	$184.84	11.745%	$206.5495	$206.55	$206.55	$206.50
Purchase #6	$183.40	11.594%	$204.6634	$204.66	$204.65	$204.70
Purchase #7	$40.98	3.496%	$42.4127	$42.41	$42.40	$42.40
7 purchase totals =	$1,189.90		$1,301.6550	$1,301.65	$1,301.65	$1,301.60