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	$244.94	6.793%	$261.5788	$261.58	$261.60	$261.60
Purchase #2	$155.38	7.248%	$166.6419	$166.64	$166.65	$166.60
Purchase #3	$246.46	7.306%	$264.4664	$264.47	$264.45	$264.50
Purchase #4	$160.80	5.416%	$169.5089	$169.51	$169.50	$169.50
Purchase #5	$79.50	12.155%	$89.1632	$89.16	$89.15	$89.20
Purchase #6	$13.25	5.453%	$13.9725	$13.97	$13.95	$14.00
Purchase #7	$35.72	8.542%	$38.7712	$38.77	$38.75	$38.80
7 purchase totals =	$936.05		$1,004.1029	$1,004.10	$1,004.05	$1,004.20