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	$12.73	12.536%	$14.3258	$14.33	$14.35	$14.30
Purchase #2	$79.58	12.831%	$89.7909	$89.79	$89.80	$89.80
Purchase #3	$97.82	11.355%	$108.9275	$108.93	$108.95	$108.90
Purchase #4	$87.41	13.805%	$99.477	$99.48	$99.50	$99.50
Purchase #5	$235.55	9.699%	$258.396	$258.40	$258.40	$258.40
Purchase #6	$146.93	4.377%	$153.3611	$153.36	$153.35	$153.40
Purchase #7	$72.33	13.463%	$82.0678	$82.07	$82.05	$82.10
7 purchase totals =	$732.35		$806.3461	$806.36	$806.40	$806.40