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	$78.80	10.307%	$86.9219	$86.92	$86.90	$86.90
Purchase #2	$127.52	12.322%	$143.233	$143.23	$143.25	$143.20
Purchase #3	$231.86	8.484%	$251.531	$251.53	$251.55	$251.50
Purchase #4	$71.31	7.459%	$76.629	$76.63	$76.65	$76.60
Purchase #5	$212.43	7.873%	$229.1546	$229.15	$229.15	$229.20
Purchase #6	$98.60	5.333%	$103.8583	$103.86	$103.85	$103.90
Purchase #7	$242.42	13.571%	$275.3188	$275.32	$275.30	$275.30
7 purchase totals =	$1,062.94		$1,166.6466	$1,166.64	$1,166.65	$1,166.60