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	$246.64	12.693%	$277.946	$277.95	$277.95	$277.90
Purchase #2	$107.45	8.478%	$116.5596	$116.56	$116.55	$116.60
Purchase #3	$199.81	5.180%	$210.1602	$210.16	$210.15	$210.20
Purchase #4	$95.60	8.353%	$103.5855	$103.59	$103.60	$103.60
Purchase #5	$155.63	4.484%	$162.6084	$162.61	$162.60	$162.60
Purchase #6	$69.52	4.731%	$72.809	$72.81	$72.80	$72.80
Purchase #7	$51.77	13.495%	$58.7564	$58.76	$58.75	$58.80
7 purchase totals =	$926.42		$1,002.4251	$1,002.44	$1,002.40	$1,002.50