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	$82.39	3.243%	$85.0619	$85.06	$85.05	$85.10
Purchase #2	$196.69	5.807%	$208.1118	$208.11	$208.10	$208.10
Purchase #3	$18.51	10.476%	$20.4491	$20.45	$20.45	$20.40
Purchase #4	$233.54	13.714%	$265.5677	$265.57	$265.55	$265.60
Purchase #5	$245.44	5.165%	$258.117	$258.12	$258.10	$258.10
Purchase #6	$35.75	7.346%	$38.3762	$38.38	$38.40	$38.40
Purchase #7	$218.43	12.481%	$245.6922	$245.69	$245.70	$245.70
7 purchase totals =	$1,030.75		$1,121.3759	$1,121.38	$1,121.35	$1,121.40