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	$225.28	8.640%	$244.7442	$244.74	$244.75	$244.70
Purchase #2	$71.42	8.459%	$77.4614	$77.46	$77.45	$77.50
Purchase #3	$64.73	4.382%	$67.5665	$67.57	$67.55	$67.60
Purchase #4	$95.85	6.533%	$102.1119	$102.11	$102.10	$102.10
Purchase #5	$19.66	11.434%	$21.9079	$21.91	$21.90	$21.90
Purchase #6	$81.66	7.638%	$87.8972	$87.90	$87.90	$87.90
Purchase #7	$86.57	4.489%	$90.4561	$90.46	$90.45	$90.50
7 purchase totals =	$645.17		$692.1452	$692.15	$692.10	$692.20