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	$105.95	3.745%	$109.9178	$109.92	$109.90	$109.90
Purchase #2	$28.83	10.260%	$31.788	$31.79	$31.80	$31.80
Purchase #3	$86.44	5.407%	$91.1138	$91.11	$91.10	$91.10
Purchase #4	$197.25	10.390%	$217.7443	$217.74	$217.75	$217.70
Purchase #5	$90.52	11.402%	$100.8411	$100.84	$100.85	$100.80
Purchase #6	$84.59	10.655%	$93.6031	$93.60	$93.60	$93.60
Purchase #7	$90.34	10.196%	$99.5511	$99.55	$99.55	$99.60
7 purchase totals =	$683.92		$744.5592	$744.55	$744.55	$744.50