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	$53.30	12.871%	$60.1602	$60.16	$60.15	$60.20
Purchase #2	$193.77	11.215%	$215.5013	$215.50	$215.50	$215.50
Purchase #3	$31.86	11.544%	$35.5379	$35.54	$35.55	$35.50
Purchase #4	$228.31	7.327%	$245.0383	$245.04	$245.05	$245.00
Purchase #5	$15.64	5.165%	$16.4478	$16.45	$16.45	$16.40
Purchase #6	$160.84	7.150%	$172.3401	$172.34	$172.35	$172.30
Purchase #7	$42.81	6.228%	$45.4762	$45.48	$45.50	$45.50
7 purchase totals =	$726.53		$790.5018	$790.51	$790.55	$790.40