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	$209.88	9.203%	$229.1953	$229.20	$229.20	$229.20
Purchase #2	$85.61	8.186%	$92.618	$92.62	$92.60	$92.60
Purchase #3	$51.53	5.579%	$54.4049	$54.40	$54.40	$54.40
Purchase #4	$19.52	10.464%	$21.5626	$21.56	$21.55	$21.60
Purchase #5	$126.44	11.402%	$140.8567	$140.86	$140.85	$140.90
Purchase #6	$105.37	12.317%	$118.3484	$118.35	$118.35	$118.30
Purchase #7	$79.44	12.636%	$89.478	$89.48	$89.50	$89.50
7 purchase totals =	$677.79		$746.4639	$746.47	$746.45	$746.50