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	$65.30	5.439%	$68.8517	$68.85	$68.85	$68.90
Purchase #2	$41.76	9.140%	$45.5769	$45.58	$45.60	$45.60
Purchase #3	$69.31	3.129%	$71.4787	$71.48	$71.50	$71.50
Purchase #4	$136.92	5.393%	$144.3041	$144.30	$144.30	$144.30
Purchase #5	$76.91	10.669%	$85.1155	$85.12	$85.10	$85.10
Purchase #6	$233.40	13.483%	$264.8693	$264.87	$264.85	$264.90
Purchase #7	$59.26	12.725%	$66.8008	$66.80	$66.80	$66.80
7 purchase totals =	$682.86		$746.9970	$747.00	$747.00	$747.10