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	$220.84	3.835%	$229.3092	$229.31	$229.30	$229.30
Purchase #2	$110.79	11.773%	$123.8333	$123.83	$123.85	$123.80
Purchase #3	$135.95	5.674%	$143.6638	$143.66	$143.65	$143.70
Purchase #4	$102.38	5.597%	$108.1102	$108.11	$108.10	$108.10
Purchase #5	$83.31	4.613%	$87.1531	$87.15	$87.15	$87.20
Purchase #6	$233.87	6.709%	$249.5603	$249.56	$249.55	$249.60
Purchase #7	$172.51	7.423%	$185.3154	$185.32	$185.30	$185.30
7 purchase totals =	$1,059.65		$1,126.9453	$1,126.94	$1,126.90	$1,127.00