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	$147.25	3.780%	$152.8161	$152.82	$152.80	$152.80
Purchase #2	$159.46	7.609%	$171.5933	$171.59	$171.60	$171.60
Purchase #3	$109.75	12.254%	$123.1988	$123.20	$123.20	$123.20
Purchase #4	$71.56	13.863%	$81.4804	$81.48	$81.50	$81.50
Purchase #5	$202.31	10.109%	$222.7615	$222.76	$222.75	$222.80
Purchase #6	$206.95	8.822%	$225.2071	$225.21	$225.20	$225.20
Purchase #7	$61.80	9.317%	$67.5579	$67.56	$67.55	$67.60
7 purchase totals =	$959.08		$1,044.6151	$1,044.62	$1,044.60	$1,044.70