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	$41.35	9.370%	$45.2245	$45.22	$45.20	$45.20
Purchase #2	$171.54	6.523%	$182.7296	$182.73	$182.75	$182.70
Purchase #3	$79.73	4.412%	$83.2477	$83.25	$83.25	$83.20
Purchase #4	$6.66	11.421%	$7.4206	$7.42	$7.40	$7.40
Purchase #5	$18.79	8.383%	$20.3652	$20.37	$20.35	$20.40
Purchase #6	$11.62	5.678%	$12.2798	$12.28	$12.30	$12.30
Purchase #7	$99.77	8.709%	$108.459	$108.46	$108.45	$108.50
7 purchase totals =	$429.46		$459.7264	$459.73	$459.70	$459.70