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	$146.89	7.772%	$158.3063	$158.31	$158.30	$158.30
Purchase #2	$190.50	4.376%	$198.8363	$198.84	$198.85	$198.80
Purchase #3	$181.83	13.143%	$205.7279	$205.73	$205.75	$205.70
Purchase #4	$235.88	5.747%	$249.436	$249.44	$249.45	$249.40
Purchase #5	$87.59	7.198%	$93.8947	$93.89	$93.90	$93.90
Purchase #6	$89.38	13.623%	$101.5562	$101.56	$101.55	$101.60
Purchase #7	$244.94	11.523%	$273.1644	$273.16	$273.15	$273.20
7 purchase totals =	$1,177.01		$1,280.9218	$1,280.93	$1,280.95	$1,280.90