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	$62.96	11.691%	$70.3207	$70.32	$70.30	$70.30
Purchase #2	$242.31	11.323%	$269.7468	$269.75	$269.75	$269.70
Purchase #3	$246.43	3.847%	$255.9102	$255.91	$255.90	$255.90
Purchase #4	$140.25	11.753%	$156.7336	$156.73	$156.75	$156.70
Purchase #5	$121.37	5.138%	$127.606	$127.61	$127.60	$127.60
Purchase #6	$18.99	4.218%	$19.791	$19.79	$19.80	$19.80
Purchase #7	$204.46	11.201%	$227.3616	$227.36	$227.35	$227.40
7 purchase totals =	$1,036.77		$1,127.4699	$1,127.47	$1,127.45	$1,127.40