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	$66.46	9.570%	$72.8202	$72.82	$72.80	$72.80
Purchase #2	$29.97	5.326%	$31.5662	$31.57	$31.55	$31.60
Purchase #3	$50.85	12.327%	$57.1183	$57.12	$57.10	$57.10
Purchase #4	$167.63	4.284%	$174.8113	$174.81	$174.80	$174.80
Purchase #5	$92.53	7.501%	$99.4707	$99.47	$99.45	$99.50
Purchase #6	$186.61	4.488%	$194.9851	$194.99	$195.00	$195.00
Purchase #7	$10.46	9.390%	$11.4422	$11.44	$11.45	$11.40
7 purchase totals =	$604.51		$642.2140	$642.22	$642.15	$642.20