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	$13.42	5.668%	$14.1806	$14.18	$14.20	$14.20
Purchase #2	$230.89	12.227%	$259.1209	$259.12	$259.10	$259.10
Purchase #3	$41.49	10.240%	$45.7386	$45.74	$45.75	$45.70
Purchase #4	$80.96	10.400%	$89.3798	$89.38	$89.40	$89.40
Purchase #5	$95.41	7.782%	$102.8348	$102.83	$102.85	$102.80
Purchase #6	$115.83	13.599%	$131.5817	$131.58	$131.60	$131.60
Purchase #7	$168.52	13.460%	$191.2028	$191.20	$191.20	$191.20
7 purchase totals =	$746.52		$834.0392	$834.03	$834.10	$834.00