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	$53.72	9.787%	$58.9776	$58.98	$59.00	$59.00
Purchase #2	$243.44	6.740%	$259.8479	$259.85	$259.85	$259.80
Purchase #3	$30.47	12.823%	$34.3772	$34.38	$34.40	$34.40
Purchase #4	$248.61	13.311%	$281.7025	$281.70	$281.70	$281.70
Purchase #5	$85.50	6.665%	$91.1986	$91.20	$91.20	$91.20
Purchase #6	$155.81	4.546%	$162.8931	$162.89	$162.90	$162.90
Purchase #7	$222.57	12.577%	$250.5626	$250.56	$250.55	$250.60
7 purchase totals =	$1,040.12		$1,139.5595	$1,139.56	$1,139.60	$1,139.60