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	$128.73	5.666%	$136.0238	$136.02	$136.00	$136.00
Purchase #2	$172.92	10.553%	$191.1682	$191.17	$191.15	$191.20
Purchase #3	$188.56	11.466%	$210.1803	$210.18	$210.20	$210.20
Purchase #4	$223.80	6.528%	$238.4097	$238.41	$238.40	$238.40
Purchase #5	$37.99	12.158%	$42.6088	$42.61	$42.60	$42.60
Purchase #6	$91.39	13.245%	$103.4946	$103.49	$103.50	$103.50
Purchase #7	$84.34	9.333%	$92.2115	$92.21	$92.20	$92.20
7 purchase totals =	$927.73		$1,014.0969	$1,014.09	$1,014.05	$1,014.10