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	$81.71	6.196%	$86.7728	$86.77	$86.75	$86.80
Purchase #2	$91.28	5.614%	$96.4045	$96.40	$96.40	$96.40
Purchase #3	$23.87	8.624%	$25.9285	$25.93	$25.95	$25.90
Purchase #4	$48.89	5.533%	$51.5951	$51.60	$51.60	$51.60
Purchase #5	$140.93	12.511%	$158.5618	$158.56	$158.55	$158.60
Purchase #6	$205.35	8.785%	$223.39	$223.39	$223.40	$223.40
Purchase #7	$48.44	3.573%	$50.1708	$50.17	$50.15	$50.20
7 purchase totals =	$640.47		$692.8235	$692.82	$692.80	$692.90