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	$62.94	6.560%	$67.0689	$67.07	$67.05	$67.10
Purchase #2	$240.55	5.857%	$254.639	$254.64	$254.65	$254.60
Purchase #3	$177.48	12.459%	$199.5922	$199.59	$199.60	$199.60
Purchase #4	$186.33	11.794%	$208.3058	$208.31	$208.30	$208.30
Purchase #5	$76.27	9.775%	$83.7254	$83.73	$83.75	$83.70
Purchase #6	$94.48	9.868%	$103.8033	$103.80	$103.80	$103.80
Purchase #7	$191.68	9.631%	$210.1407	$210.14	$210.15	$210.10
7 purchase totals =	$1,029.73		$1,127.2753	$1,127.28	$1,127.30	$1,127.20