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	$161.82	4.311%	$168.7961	$168.80	$168.80	$168.80
Purchase #2	$26.76	7.280%	$28.7081	$28.71	$28.70	$28.70
Purchase #3	$49.86	10.835%	$55.2623	$55.26	$55.25	$55.30
Purchase #4	$83.27	9.824%	$91.4504	$91.45	$91.45	$91.50
Purchase #5	$184.72	11.281%	$205.5583	$205.56	$205.55	$205.60
Purchase #6	$26.48	7.125%	$28.3667	$28.37	$28.35	$28.40
Purchase #7	$10.54	13.841%	$11.9988	$12.00	$12.00	$12.00
7 purchase totals =	$543.45		$590.1407	$590.15	$590.10	$590.30