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	$95.57	10.399%	$105.5083	$105.51	$105.50	$105.50
Purchase #2	$40.43	12.539%	$45.4995	$45.50	$45.50	$45.50
Purchase #3	$131.48	7.400%	$141.2095	$141.21	$141.20	$141.20
Purchase #4	$25.33	4.253%	$26.4073	$26.41	$26.40	$26.40
Purchase #5	$42.51	6.689%	$45.3535	$45.35	$45.35	$45.40
Purchase #6	$205.28	4.826%	$215.1868	$215.19	$215.20	$215.20
Purchase #7	$120.42	5.131%	$126.5988	$126.60	$126.60	$126.60
7 purchase totals =	$661.02		$705.7637	$705.77	$705.75	$705.80