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	$196.59	11.864%	$219.9134	$219.91	$219.90	$219.90
Purchase #2	$150.28	13.730%	$170.9134	$170.91	$170.90	$170.90
Purchase #3	$130.47	8.269%	$141.2586	$141.26	$141.25	$141.30
Purchase #4	$165.25	8.128%	$178.6815	$178.68	$178.70	$178.70
Purchase #5	$207.68	7.409%	$223.067	$223.07	$223.05	$223.10
Purchase #6	$103.89	5.772%	$109.8865	$109.89	$109.90	$109.90
Purchase #7	$98.55	9.326%	$107.7408	$107.74	$107.75	$107.70
7 purchase totals =	$1,052.71		$1,151.4612	$1,151.46	$1,151.45	$1,151.50