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	$13.39	5.367%	$14.1086	$14.11	$14.10	$14.10
Purchase #2	$186.35	3.465%	$192.807	$192.81	$192.80	$192.80
Purchase #3	$179.71	6.501%	$191.3929	$191.39	$191.40	$191.40
Purchase #4	$68.53	12.526%	$77.1141	$77.11	$77.10	$77.10
Purchase #5	$209.50	11.260%	$233.0897	$233.09	$233.10	$233.10
Purchase #6	$95.94	10.181%	$105.7077	$105.71	$105.70	$105.70
Purchase #7	$220.50	13.600%	$250.488	$250.49	$250.50	$250.50
7 purchase totals =	$973.92		$1,064.7080	$1,064.71	$1,064.70	$1,064.70