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	$99.82	3.567%	$103.3806	$103.38	$103.40	$103.40
Purchase #2	$137.94	6.376%	$146.7351	$146.74	$146.75	$146.70
Purchase #3	$137.30	9.644%	$150.5412	$150.54	$150.55	$150.50
Purchase #4	$86.32	7.662%	$92.9338	$92.93	$92.95	$92.90
Purchase #5	$67.84	10.132%	$74.7135	$74.71	$74.70	$74.70
Purchase #6	$102.71	10.480%	$113.474	$113.47	$113.45	$113.50
Purchase #7	$192.59	11.789%	$215.2944	$215.29	$215.30	$215.30
7 purchase totals =	$824.52		$897.0726	$897.06	$897.10	$897.00