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	$198.69	6.151%	$210.9114	$210.91	$210.90	$210.90
Purchase #2	$171.55	9.685%	$188.1646	$188.16	$188.15	$188.20
Purchase #3	$127.59	10.648%	$141.1758	$141.18	$141.20	$141.20
Purchase #4	$6.87	13.403%	$7.7908	$7.79	$7.80	$7.80
Purchase #5	$64.68	11.278%	$71.9746	$71.97	$71.95	$72.00
Purchase #6	$115.82	3.555%	$119.9374	$119.94	$119.95	$119.90
Purchase #7	$168.66	3.528%	$174.6103	$174.61	$174.60	$174.60
7 purchase totals =	$853.86		$914.5649	$914.56	$914.55	$914.60