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	$197.27	13.465%	$223.8324	$223.83	$223.85	$223.80
Purchase #2	$113.71	13.104%	$128.6106	$128.61	$128.60	$128.60
Purchase #3	$19.66	6.233%	$20.8854	$20.89	$20.90	$20.90
Purchase #4	$147.42	7.129%	$157.9296	$157.93	$157.95	$157.90
Purchase #5	$91.63	12.553%	$103.1323	$103.13	$103.15	$103.10
Purchase #6	$165.50	13.429%	$187.725	$187.73	$187.75	$187.70
Purchase #7	$165.41	8.769%	$179.9148	$179.91	$179.90	$179.90
7 purchase totals =	$900.60		$1,002.0301	$1,002.03	$1,002.10	$1,001.90