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	$83.86	10.269%	$92.4716	$92.47	$92.45	$92.50
Purchase #2	$98.30	3.312%	$101.5557	$101.56	$101.55	$101.60
Purchase #3	$31.38	3.614%	$32.5141	$32.51	$32.50	$32.50
Purchase #4	$198.41	12.422%	$223.0565	$223.06	$223.05	$223.10
Purchase #5	$9.45	10.760%	$10.4668	$10.47	$10.45	$10.50
Purchase #6	$237.75	5.113%	$249.9062	$249.91	$249.90	$249.90
Purchase #7	$153.79	3.871%	$159.7432	$159.74	$159.75	$159.70
7 purchase totals =	$812.94		$869.7141	$869.72	$869.65	$869.80