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	$228.87	10.561%	$253.041	$253.04	$253.05	$253.00
Purchase #2	$102.36	11.382%	$114.0106	$114.01	$114.00	$114.00
Purchase #3	$53.55	6.108%	$56.8208	$56.82	$56.80	$56.80
Purchase #4	$195.85	13.179%	$221.6611	$221.66	$221.65	$221.70
Purchase #5	$139.74	9.110%	$152.4703	$152.47	$152.45	$152.50
Purchase #6	$53.30	13.528%	$60.5104	$60.51	$60.50	$60.50
Purchase #7	$241.89	3.540%	$250.4529	$250.45	$250.45	$250.50
7 purchase totals =	$1,015.56		$1,108.9671	$1,108.96	$1,108.90	$1,109.00