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	$168.75	12.741%	$190.2504	$190.25	$190.25	$190.30
Purchase #2	$161.31	3.114%	$166.3332	$166.33	$166.35	$166.30
Purchase #3	$27.72	13.118%	$31.3563	$31.36	$31.35	$31.40
Purchase #4	$205.57	11.606%	$229.4285	$229.43	$229.45	$229.40
Purchase #5	$153.40	4.641%	$160.5193	$160.52	$160.50	$160.50
Purchase #6	$91.92	11.336%	$102.3401	$102.34	$102.35	$102.30
Purchase #7	$16.29	3.697%	$16.8922	$16.89	$16.90	$16.90
7 purchase totals =	$824.96		$897.1200	$897.12	$897.15	$897.10