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	$195.65	12.521%	$220.1473	$220.15	$220.15	$220.10
Purchase #2	$40.95	7.288%	$43.9344	$43.93	$43.95	$43.90
Purchase #3	$43.47	4.852%	$45.5792	$45.58	$45.60	$45.60
Purchase #4	$150.27	6.111%	$159.453	$159.45	$159.45	$159.50
Purchase #5	$194.73	10.711%	$215.5875	$215.59	$215.60	$215.60
Purchase #6	$243.31	7.704%	$262.0546	$262.05	$262.05	$262.10
Purchase #7	$82.50	9.813%	$90.5957	$90.60	$90.60	$90.60
7 purchase totals =	$950.88		$1,037.3517	$1,037.35	$1,037.40	$1,037.40