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	$100.63	4.709%	$105.3687	$105.37	$105.35	$105.40
Purchase #2	$229.90	4.739%	$240.795	$240.80	$240.80	$240.80
Purchase #3	$142.48	6.441%	$151.6571	$151.66	$151.65	$151.70
Purchase #4	$206.46	4.454%	$215.6557	$215.66	$215.65	$215.70
Purchase #5	$243.85	6.557%	$259.8392	$259.84	$259.85	$259.80
Purchase #6	$145.79	13.189%	$165.0182	$165.02	$165.00	$165.00
Purchase #7	$152.70	13.407%	$173.1725	$173.17	$173.15	$173.20
7 purchase totals =	$1,221.81		$1,311.5064	$1,311.52	$1,311.45	$1,311.60