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	$164.99	3.662%	$171.0319	$171.03	$171.05	$171.00
Purchase #2	$17.39	5.451%	$18.3379	$18.34	$18.35	$18.30
Purchase #3	$140.57	3.231%	$145.1118	$145.11	$145.10	$145.10
Purchase #4	$18.64	10.279%	$20.556	$20.56	$20.55	$20.60
Purchase #5	$75.28	9.365%	$82.33	$82.33	$82.35	$82.30
Purchase #6	$146.63	7.782%	$158.0407	$158.04	$158.05	$158.00
Purchase #7	$90.52	13.597%	$102.828	$102.83	$102.85	$102.80
7 purchase totals =	$654.02		$698.2363	$698.24	$698.30	$698.10