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	$59.74	9.279%	$65.2833	$65.28	$65.30	$65.30
Purchase #2	$89.35	3.431%	$92.4156	$92.42	$92.40	$92.40
Purchase #3	$64.69	12.562%	$72.8164	$72.82	$72.80	$72.80
Purchase #4	$189.33	5.427%	$199.6049	$199.60	$199.60	$199.60
Purchase #5	$29.71	6.327%	$31.5898	$31.59	$31.60	$31.60
Purchase #6	$171.25	8.260%	$185.3953	$185.40	$185.40	$185.40
Purchase #7	$167.45	7.300%	$179.6739	$179.67	$179.65	$179.70
7 purchase totals =	$771.52		$826.7792	$826.78	$826.75	$826.80