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	$217.96	13.478%	$247.3366	$247.34	$247.35	$247.30
Purchase #2	$173.82	6.588%	$185.2713	$185.27	$185.25	$185.30
Purchase #3	$225.74	10.473%	$249.3818	$249.38	$249.40	$249.40
Purchase #4	$70.65	8.728%	$76.8163	$76.82	$76.80	$76.80
Purchase #5	$165.28	4.614%	$172.906	$172.91	$172.90	$172.90
Purchase #6	$36.96	5.873%	$39.1307	$39.13	$39.15	$39.10
Purchase #7	$31.54	10.705%	$34.9164	$34.92	$34.90	$34.90
7 purchase totals =	$921.95		$1,005.7591	$1,005.77	$1,005.75	$1,005.70