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	$119.29	6.610%	$127.1751	$127.18	$127.20	$127.20
Purchase #2	$169.41	7.174%	$181.5635	$181.56	$181.55	$181.60
Purchase #3	$162.51	10.712%	$179.9181	$179.92	$179.90	$179.90
Purchase #4	$53.37	8.355%	$57.8291	$57.83	$57.85	$57.80
Purchase #5	$89.93	7.375%	$96.5623	$96.56	$96.55	$96.60
Purchase #6	$232.76	10.817%	$257.9376	$257.94	$257.95	$257.90
Purchase #7	$211.25	13.357%	$239.4667	$239.47	$239.45	$239.50
7 purchase totals =	$1,038.52		$1,140.4524	$1,140.46	$1,140.45	$1,140.50