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	$56.82	4.182%	$59.1962	$59.20	$59.20	$59.20
Purchase #2	$198.57	7.473%	$213.4091	$213.41	$213.40	$213.40
Purchase #3	$240.64	11.479%	$268.2631	$268.26	$268.25	$268.30
Purchase #4	$85.44	11.239%	$95.0426	$95.04	$95.05	$95.00
Purchase #5	$247.56	9.286%	$270.5484	$270.55	$270.55	$270.50
Purchase #6	$172.54	10.254%	$190.2323	$190.23	$190.25	$190.20
Purchase #7	$166.43	13.496%	$188.8914	$188.89	$188.90	$188.90
7 purchase totals =	$1,168.00		$1,285.5831	$1,285.58	$1,285.60	$1,285.50