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	$201.89	3.715%	$209.3902	$209.39	$209.40	$209.40
Purchase #2	$27.51	13.594%	$31.2497	$31.25	$31.25	$31.20
Purchase #3	$243.38	4.136%	$253.4462	$253.45	$253.45	$253.40
Purchase #4	$244.76	13.794%	$278.5222	$278.52	$278.50	$278.50
Purchase #5	$80.28	9.653%	$88.0294	$88.03	$88.05	$88.00
Purchase #6	$117.80	4.384%	$122.9644	$122.96	$122.95	$123.00
Purchase #7	$55.48	7.182%	$59.4646	$59.46	$59.45	$59.50
7 purchase totals =	$971.10		$1,043.0667	$1,043.06	$1,043.05	$1,043.00