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	$134.29	8.641%	$145.894	$145.89	$145.90	$145.90
Purchase #2	$219.79	11.470%	$244.9999	$245.00	$245.00	$245.00
Purchase #3	$137.82	10.872%	$152.8038	$152.80	$152.80	$152.80
Purchase #4	$75.27	6.770%	$80.3658	$80.37	$80.35	$80.40
Purchase #5	$16.78	11.124%	$18.6466	$18.65	$18.65	$18.60
Purchase #6	$215.47	11.769%	$240.8287	$240.83	$240.85	$240.80
Purchase #7	$212.70	4.707%	$222.7118	$222.71	$222.70	$222.70
7 purchase totals =	$1,012.12		$1,106.2506	$1,106.25	$1,106.25	$1,106.20