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	$195.95	8.392%	$212.3941	$212.39	$212.40	$212.40
Purchase #2	$30.72	4.539%	$32.1144	$32.11	$32.10	$32.10
Purchase #3	$99.63	13.309%	$112.8898	$112.89	$112.90	$112.90
Purchase #4	$148.45	9.407%	$162.4147	$162.41	$162.40	$162.40
Purchase #5	$34.57	10.491%	$38.1967	$38.20	$38.20	$38.20
Purchase #6	$80.46	12.329%	$90.3799	$90.38	$90.40	$90.40
Purchase #7	$33.98	3.784%	$35.2658	$35.27	$35.25	$35.30
7 purchase totals =	$623.76		$683.6554	$683.65	$683.65	$683.70