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	$210.81	5.408%	$222.2106	$222.21	$222.20	$222.20
Purchase #2	$206.39	13.205%	$233.6438	$233.64	$233.65	$233.60
Purchase #3	$68.85	5.451%	$72.603	$72.60	$72.60	$72.60
Purchase #4	$148.49	11.500%	$165.5664	$165.57	$165.55	$165.60
Purchase #5	$212.27	13.459%	$240.8394	$240.84	$240.85	$240.80
Purchase #6	$47.39	7.235%	$50.8187	$50.82	$50.80	$50.80
Purchase #7	$21.48	12.788%	$24.2269	$24.23	$24.25	$24.20
7 purchase totals =	$915.68		$1,009.9088	$1,009.91	$1,009.90	$1,009.80