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	$149.80	11.719%	$167.3551	$167.36	$167.35	$167.40
Purchase #2	$223.44	7.812%	$240.8951	$240.90	$240.90	$240.90
Purchase #3	$138.57	9.639%	$151.9268	$151.93	$151.95	$151.90
Purchase #4	$15.42	10.286%	$17.0061	$17.01	$17.00	$17.00
Purchase #5	$63.59	13.818%	$72.3769	$72.38	$72.40	$72.40
Purchase #6	$122.82	11.784%	$137.2931	$137.29	$137.30	$137.30
Purchase #7	$245.28	7.845%	$264.5222	$264.52	$264.50	$264.50
7 purchase totals =	$958.92		$1,051.3753	$1,051.39	$1,051.40	$1,051.40