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	$176.59	7.268%	$189.4246	$189.42	$189.40	$189.40
Purchase #2	$6.77	13.383%	$7.676	$7.68	$7.70	$7.70
Purchase #3	$176.86	8.406%	$191.7269	$191.73	$191.75	$191.70
Purchase #4	$44.72	9.816%	$49.1097	$49.11	$49.10	$49.10
Purchase #5	$53.33	12.156%	$59.8128	$59.81	$59.80	$59.80
Purchase #6	$210.35	10.803%	$233.0741	$233.07	$233.05	$233.10
Purchase #7	$248.60	12.140%	$278.78	$278.78	$278.80	$278.80
7 purchase totals =	$917.22		$1,009.6041	$1,009.60	$1,009.60	$1,009.60