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	$103.25	6.610%	$110.0748	$110.07	$110.05	$110.10
Purchase #2	$14.47	4.555%	$15.1291	$15.13	$15.15	$15.10
Purchase #3	$160.29	13.475%	$181.8891	$181.89	$181.90	$181.90
Purchase #4	$55.65	7.518%	$59.8338	$59.83	$59.85	$59.80
Purchase #5	$46.34	6.407%	$49.309	$49.31	$49.30	$49.30
Purchase #6	$167.61	12.415%	$188.4188	$188.42	$188.40	$188.40
Purchase #7	$44.40	9.745%	$48.7268	$48.73	$48.75	$48.70
7 purchase totals =	$592.01		$653.3814	$653.38	$653.40	$653.30