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	$204.86	11.569%	$228.5603	$228.56	$228.55	$228.60
Purchase #2	$104.95	5.785%	$111.0214	$111.02	$111.00	$111.00
Purchase #3	$215.28	3.502%	$222.8191	$222.82	$222.80	$222.80
Purchase #4	$124.27	13.275%	$140.7668	$140.77	$140.75	$140.80
Purchase #5	$161.91	12.162%	$181.6015	$181.60	$181.60	$181.60
Purchase #6	$81.57	11.592%	$91.0256	$91.03	$91.05	$91.00
Purchase #7	$160.36	8.210%	$173.5256	$173.53	$173.55	$173.50
7 purchase totals =	$1,053.20		$1,149.3203	$1,149.33	$1,149.30	$1,149.30