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	$208.89	7.669%	$224.9098	$224.91	$224.90	$224.90
Purchase #2	$92.38	10.660%	$102.2277	$102.23	$102.25	$102.20
Purchase #3	$99.82	5.599%	$105.4089	$105.41	$105.40	$105.40
Purchase #4	$83.83	6.575%	$89.3418	$89.34	$89.35	$89.30
Purchase #5	$8.56	9.586%	$9.3806	$9.38	$9.40	$9.40
Purchase #6	$247.88	10.751%	$274.5296	$274.53	$274.55	$274.50
Purchase #7	$84.36	6.445%	$89.797	$89.80	$89.80	$89.80
7 purchase totals =	$825.72		$895.5954	$895.60	$895.65	$895.50