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	$98.45	3.429%	$101.8259	$101.83	$101.85	$101.80
Purchase #2	$130.76	4.551%	$136.7109	$136.71	$136.70	$136.70
Purchase #3	$226.64	13.372%	$256.9463	$256.95	$256.95	$256.90
Purchase #4	$178.76	8.411%	$193.7955	$193.80	$193.80	$193.80
Purchase #5	$73.79	6.243%	$78.3967	$78.40	$78.40	$78.40
Purchase #6	$144.77	10.532%	$160.0172	$160.02	$160.00	$160.00
Purchase #7	$114.86	7.537%	$123.517	$123.52	$123.50	$123.50
7 purchase totals =	$968.03		$1,051.2095	$1,051.23	$1,051.20	$1,051.10