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	$215.83	3.223%	$222.7862	$222.79	$222.80	$222.80
Purchase #2	$243.57	3.269%	$251.5323	$251.53	$251.55	$251.50
Purchase #3	$130.80	9.764%	$143.5713	$143.57	$143.55	$143.60
Purchase #4	$87.90	4.495%	$91.8511	$91.85	$91.85	$91.90
Purchase #5	$121.95	4.275%	$127.1634	$127.16	$127.15	$127.20
Purchase #6	$32.90	4.841%	$34.4927	$34.49	$34.50	$34.50
Purchase #7	$218.89	8.474%	$237.4387	$237.44	$237.45	$237.40
7 purchase totals =	$1,051.84		$1,108.8357	$1,108.83	$1,108.85	$1,108.90