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	$198.64	3.862%	$206.3115	$206.31	$206.30	$206.30
Purchase #2	$103.57	8.292%	$112.158	$112.16	$112.15	$112.20
Purchase #3	$202.55	4.385%	$211.4318	$211.43	$211.45	$211.40
Purchase #4	$140.94	11.365%	$156.9578	$156.96	$156.95	$157.00
Purchase #5	$124.40	6.482%	$132.4636	$132.46	$132.45	$132.50
Purchase #6	$37.88	13.810%	$43.1112	$43.11	$43.10	$43.10
Purchase #7	$234.40	3.554%	$242.7306	$242.73	$242.75	$242.70
7 purchase totals =	$1,042.38		$1,105.1645	$1,105.16	$1,105.15	$1,105.20