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	$22.97	3.692%	$23.8181	$23.82	$23.80	$23.80
Purchase #2	$201.77	10.669%	$223.2968	$223.30	$223.30	$223.30
Purchase #3	$106.77	10.104%	$117.558	$117.56	$117.55	$117.60
Purchase #4	$111.93	5.639%	$118.2417	$118.24	$118.25	$118.20
Purchase #5	$232.35	10.555%	$256.8745	$256.87	$256.85	$256.90
Purchase #6	$130.40	9.313%	$142.5442	$142.54	$142.55	$142.50
Purchase #7	$167.26	7.279%	$179.4349	$179.43	$179.45	$179.40
7 purchase totals =	$973.45		$1,061.7682	$1,061.76	$1,061.75	$1,061.70