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	$139.64	9.736%	$153.2354	$153.24	$153.25	$153.20
Purchase #2	$56.91	4.851%	$59.6707	$59.67	$59.65	$59.70
Purchase #3	$89.60	5.839%	$94.8317	$94.83	$94.85	$94.80
Purchase #4	$30.54	4.802%	$32.0065	$32.01	$32.00	$32.00
Purchase #5	$139.81	5.839%	$147.9735	$147.97	$147.95	$148.00
Purchase #6	$207.74	7.555%	$223.4348	$223.43	$223.45	$223.40
Purchase #7	$16.28	13.457%	$18.4708	$18.47	$18.45	$18.50
7 purchase totals =	$680.52		$729.6234	$729.62	$729.60	$729.60