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	$145.40	10.142%	$160.1465	$160.15	$160.15	$160.10
Purchase #2	$135.71	12.180%	$152.2395	$152.24	$152.25	$152.20
Purchase #3	$73.73	4.634%	$77.1466	$77.15	$77.15	$77.10
Purchase #4	$71.75	9.128%	$78.2993	$78.30	$78.30	$78.30
Purchase #5	$230.52	6.780%	$246.1493	$246.15	$246.15	$246.10
Purchase #6	$162.56	11.355%	$181.0187	$181.02	$181.00	$181.00
Purchase #7	$50.51	10.472%	$55.7994	$55.80	$55.80	$55.80
7 purchase totals =	$870.18		$950.7993	$950.81	$950.80	$950.60