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	$188.50	4.171%	$196.3623	$196.36	$196.35	$196.40
Purchase #2	$209.76	4.334%	$218.851	$218.85	$218.85	$218.90
Purchase #3	$5.34	13.718%	$6.0725	$6.07	$6.05	$6.10
Purchase #4	$35.25	5.569%	$37.2131	$37.21	$37.20	$37.20
Purchase #5	$37.83	6.425%	$40.2606	$40.26	$40.25	$40.30
Purchase #6	$239.88	13.862%	$273.1322	$273.13	$273.15	$273.10
Purchase #7	$48.76	10.721%	$53.9876	$53.99	$54.00	$54.00
7 purchase totals =	$765.32		$825.8793	$825.87	$825.85	$826.00