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	$101.65	4.736%	$106.4641	$106.46	$106.45	$106.50
Purchase #2	$91.78	3.599%	$95.0832	$95.08	$95.10	$95.10
Purchase #3	$55.56	9.584%	$60.8849	$60.88	$60.90	$60.90
Purchase #4	$84.91	6.557%	$90.4775	$90.48	$90.50	$90.50
Purchase #5	$245.96	10.590%	$272.0072	$272.01	$272.00	$272.00
Purchase #6	$26.58	7.469%	$28.5653	$28.57	$28.55	$28.60
Purchase #7	$82.40	9.415%	$90.158	$90.16	$90.15	$90.20
7 purchase totals =	$688.84		$743.6402	$743.64	$743.65	$743.80