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	$181.68	12.202%	$203.8486	$203.85	$203.85	$203.80
Purchase #2	$74.71	4.598%	$78.1452	$78.15	$78.15	$78.10
Purchase #3	$142.85	6.514%	$152.1552	$152.16	$152.15	$152.20
Purchase #4	$72.64	11.653%	$81.1047	$81.10	$81.10	$81.10
Purchase #5	$77.52	6.381%	$82.4666	$82.47	$82.45	$82.50
Purchase #6	$85.59	6.759%	$91.375	$91.38	$91.40	$91.40
Purchase #7	$29.92	10.326%	$33.0095	$33.01	$33.00	$33.00
7 purchase totals =	$664.91		$722.1048	$722.12	$722.10	$722.10