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	$85.88	11.202%	$95.5003	$95.50	$95.50	$95.50
Purchase #2	$48.85	6.180%	$51.8689	$51.87	$51.85	$51.90
Purchase #3	$100.65	9.705%	$110.4181	$110.42	$110.40	$110.40
Purchase #4	$51.80	10.594%	$57.2877	$57.29	$57.30	$57.30
Purchase #5	$77.94	5.865%	$82.5112	$82.51	$82.50	$82.50
Purchase #6	$51.33	11.365%	$57.1637	$57.16	$57.15	$57.20
Purchase #7	$123.30	11.603%	$137.6065	$137.61	$137.60	$137.60
7 purchase totals =	$539.75		$592.3564	$592.36	$592.30	$592.40