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	$100.26	5.625%	$105.8996	$105.90	$105.90	$105.90
Purchase #2	$51.34	5.850%	$54.3434	$54.34	$54.35	$54.30
Purchase #3	$59.45	8.391%	$64.4384	$64.44	$64.45	$64.40
Purchase #4	$243.35	9.819%	$267.2445	$267.24	$267.25	$267.20
Purchase #5	$151.90	11.144%	$168.8277	$168.83	$168.85	$168.80
Purchase #6	$245.86	12.504%	$276.6023	$276.60	$276.60	$276.60
Purchase #7	$204.33	5.566%	$215.703	$215.70	$215.70	$215.70
7 purchase totals =	$1,056.49		$1,153.0589	$1,153.05	$1,153.10	$1,152.90