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	$129.56	3.760%	$134.4315	$134.43	$134.45	$134.40
Purchase #2	$228.48	5.413%	$240.8476	$240.85	$240.85	$240.80
Purchase #3	$235.85	3.862%	$244.9585	$244.96	$244.95	$245.00
Purchase #4	$65.79	10.122%	$72.4493	$72.45	$72.45	$72.40
Purchase #5	$164.85	10.498%	$182.156	$182.16	$182.15	$182.20
Purchase #6	$115.35	4.118%	$120.1001	$120.10	$120.10	$120.10
Purchase #7	$231.91	12.786%	$261.562	$261.56	$261.55	$261.60
7 purchase totals =	$1,171.79		$1,256.5050	$1,256.51	$1,256.50	$1,256.50