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	$69.90	11.753%	$78.1153	$78.12	$78.10	$78.10
Purchase #2	$65.27	12.663%	$73.5351	$73.54	$73.55	$73.50
Purchase #3	$8.88	13.232%	$10.055	$10.06	$10.05	$10.10
Purchase #4	$45.67	7.107%	$48.9158	$48.92	$48.90	$48.90
Purchase #5	$118.85	3.652%	$123.1904	$123.19	$123.20	$123.20
Purchase #6	$55.25	13.412%	$62.6601	$62.66	$62.65	$62.70
Purchase #7	$99.61	9.316%	$108.8897	$108.89	$108.90	$108.90
7 purchase totals =	$463.43		$505.3614	$505.38	$505.35	$505.40