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	$149.34	10.501%	$165.0222	$165.02	$165.00	$165.00
Purchase #2	$181.85	12.850%	$205.2177	$205.22	$205.20	$205.20
Purchase #3	$48.40	4.844%	$50.7445	$50.74	$50.75	$50.70
Purchase #4	$248.85	9.685%	$272.9511	$272.95	$272.95	$273.00
Purchase #5	$52.71	3.167%	$54.3793	$54.38	$54.40	$54.40
Purchase #6	$241.43	5.769%	$255.3581	$255.36	$255.35	$255.40
Purchase #7	$201.55	10.250%	$222.2089	$222.21	$222.20	$222.20
7 purchase totals =	$1,124.13		$1,225.8818	$1,225.88	$1,225.85	$1,225.90