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	$250.54	10.169%	$276.0174	$276.02	$276.00	$276.00
Purchase #2	$34.76	10.302%	$38.341	$38.34	$38.35	$38.30
Purchase #3	$153.25	6.127%	$162.6396	$162.64	$162.65	$162.60
Purchase #4	$149.98	10.325%	$165.4654	$165.47	$165.45	$165.50
Purchase #5	$226.98	9.206%	$247.8758	$247.88	$247.90	$247.90
Purchase #6	$122.87	11.180%	$136.6069	$136.61	$136.60	$136.60
Purchase #7	$33.77	3.663%	$35.007	$35.01	$35.00	$35.00
7 purchase totals =	$972.15		$1,061.9531	$1,061.97	$1,061.95	$1,061.90