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	$151.66	10.153%	$167.058	$167.06	$167.05	$167.10
Purchase #2	$11.42	4.742%	$11.9615	$11.96	$11.95	$12.00
Purchase #3	$119.69	12.361%	$134.4849	$134.48	$134.50	$134.50
Purchase #4	$32.25	10.277%	$35.5643	$35.56	$35.55	$35.60
Purchase #5	$13.40	6.737%	$14.3028	$14.30	$14.30	$14.30
Purchase #6	$81.45	9.872%	$89.4907	$89.49	$89.50	$89.50
Purchase #7	$233.51	9.540%	$255.7869	$255.79	$255.80	$255.80
7 purchase totals =	$643.38		$708.6491	$708.64	$708.65	$708.80