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	$245.49	12.213%	$275.4717	$275.47	$275.45	$275.50
Purchase #2	$100.85	5.169%	$106.0629	$106.06	$106.05	$106.10
Purchase #3	$145.72	6.527%	$155.2311	$155.23	$155.25	$155.20
Purchase #4	$107.33	11.134%	$119.2801	$119.28	$119.30	$119.30
Purchase #5	$81.29	3.237%	$83.9214	$83.92	$83.90	$83.90
Purchase #6	$178.66	11.318%	$198.8807	$198.88	$198.90	$198.90
Purchase #7	$83.48	11.546%	$93.1186	$93.12	$93.10	$93.10
7 purchase totals =	$942.82		$1,031.9665	$1,031.96	$1,031.95	$1,032.00