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	$204.71	7.120%	$219.2854	$219.29	$219.30	$219.30
Purchase #2	$13.42	6.492%	$14.2912	$14.29	$14.30	$14.30
Purchase #3	$215.74	7.299%	$231.4869	$231.49	$231.50	$231.50
Purchase #4	$79.86	3.395%	$82.5712	$82.57	$82.55	$82.60
Purchase #5	$66.77	6.368%	$71.0219	$71.02	$71.00	$71.00
Purchase #6	$33.78	13.388%	$38.3025	$38.30	$38.30	$38.30
Purchase #7	$99.63	4.824%	$104.4362	$104.44	$104.45	$104.40
7 purchase totals =	$713.91		$761.3953	$761.40	$761.40	$761.40