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	$142.44	7.482%	$153.0974	$153.10	$153.10	$153.10
Purchase #2	$180.49	3.748%	$187.2548	$187.25	$187.25	$187.30
Purchase #3	$26.72	7.779%	$28.7985	$28.80	$28.80	$28.80
Purchase #4	$79.48	3.526%	$82.2825	$82.28	$82.30	$82.30
Purchase #5	$191.55	13.413%	$217.2426	$217.24	$217.25	$217.20
Purchase #6	$194.26	11.445%	$216.4931	$216.49	$216.50	$216.50
Purchase #7	$33.88	10.685%	$37.5001	$37.50	$37.50	$37.50
7 purchase totals =	$848.82		$922.6690	$922.66	$922.70	$922.70