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	$63.53	7.522%	$68.3087	$68.31	$68.30	$68.30
Purchase #2	$33.52	4.653%	$35.0797	$35.08	$35.10	$35.10
Purchase #3	$164.83	9.866%	$181.0921	$181.09	$181.10	$181.10
Purchase #4	$222.32	9.696%	$243.8761	$243.88	$243.90	$243.90
Purchase #5	$217.88	9.516%	$238.6135	$238.61	$238.60	$238.60
Purchase #6	$142.61	12.121%	$159.8958	$159.90	$159.90	$159.90
Purchase #7	$220.93	11.295%	$245.884	$245.88	$245.90	$245.90
7 purchase totals =	$1,065.62		$1,172.7499	$1,172.75	$1,172.80	$1,172.80