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	$221.53	5.581%	$233.8936	$233.89	$233.90	$233.90
Purchase #2	$20.45	12.141%	$22.9328	$22.93	$22.95	$22.90
Purchase #3	$189.65	6.285%	$201.5695	$201.57	$201.55	$201.60
Purchase #4	$145.74	10.326%	$160.7891	$160.79	$160.80	$160.80
Purchase #5	$117.46	8.446%	$127.3807	$127.38	$127.40	$127.40
Purchase #6	$201.71	3.195%	$208.1546	$208.15	$208.15	$208.20
Purchase #7	$85.74	5.445%	$90.4085	$90.41	$90.40	$90.40
7 purchase totals =	$982.28		$1,045.1288	$1,045.12	$1,045.15	$1,045.20