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	$103.93	6.746%	$110.9411	$110.94	$110.95	$110.90
Purchase #2	$212.63	7.635%	$228.8643	$228.86	$228.85	$228.90
Purchase #3	$169.98	9.584%	$186.2709	$186.27	$186.25	$186.30
Purchase #4	$76.35	7.603%	$82.1549	$82.15	$82.15	$82.20
Purchase #5	$90.91	10.676%	$100.6156	$100.62	$100.60	$100.60
Purchase #6	$176.72	4.580%	$184.8138	$184.81	$184.80	$184.80
Purchase #7	$45.33	5.143%	$47.6613	$47.66	$47.65	$47.70
7 purchase totals =	$875.85		$941.3219	$941.31	$941.25	$941.40