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	$181.87	5.334%	$191.5709	$191.57	$191.55	$191.60
Purchase #2	$156.48	13.759%	$178.0101	$178.01	$178.00	$178.00
Purchase #3	$58.82	4.668%	$61.5657	$61.57	$61.55	$61.60
Purchase #4	$241.92	11.337%	$269.3465	$269.35	$269.35	$269.30
Purchase #5	$130.50	11.717%	$145.7907	$145.79	$145.80	$145.80
Purchase #6	$107.89	3.433%	$111.5939	$111.59	$111.60	$111.60
Purchase #7	$6.76	9.135%	$7.3775	$7.38	$7.40	$7.40
7 purchase totals =	$884.24		$965.2553	$965.26	$965.25	$965.30