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	$92.25	3.578%	$95.5507	$95.55	$95.55	$95.60
Purchase #2	$184.27	3.568%	$190.8448	$190.84	$190.85	$190.80
Purchase #3	$85.61	5.241%	$90.0968	$90.10	$90.10	$90.10
Purchase #4	$129.50	9.752%	$142.1288	$142.13	$142.15	$142.10
Purchase #5	$103.73	12.590%	$116.7896	$116.79	$116.80	$116.80
Purchase #6	$76.63	9.712%	$84.0723	$84.07	$84.05	$84.10
Purchase #7	$20.41	4.570%	$21.3427	$21.34	$21.35	$21.30
7 purchase totals =	$692.40		$740.8257	$740.82	$740.85	$740.80