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	$63.66	11.581%	$71.0325	$71.03	$71.05	$71.00
Purchase #2	$245.57	3.176%	$253.3693	$253.37	$253.35	$253.40
Purchase #3	$147.54	8.185%	$159.6161	$159.62	$159.60	$159.60
Purchase #4	$84.57	9.682%	$92.7581	$92.76	$92.75	$92.80
Purchase #5	$74.54	10.686%	$82.5053	$82.51	$82.50	$82.50
Purchase #6	$155.86	9.369%	$170.4625	$170.46	$170.45	$170.50
Purchase #7	$165.61	10.369%	$182.7821	$182.78	$182.80	$182.80
7 purchase totals =	$937.35		$1,012.5259	$1,012.53	$1,012.50	$1,012.60