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	$64.56	11.348%	$71.8863	$71.89	$71.90	$71.90
Purchase #2	$197.62	11.413%	$220.1744	$220.17	$220.15	$220.20
Purchase #3	$193.54	8.810%	$210.5909	$210.59	$210.60	$210.60
Purchase #4	$166.37	3.515%	$172.2179	$172.22	$172.20	$172.20
Purchase #5	$207.85	3.112%	$214.3183	$214.32	$214.30	$214.30
Purchase #6	$135.65	12.361%	$152.4177	$152.42	$152.40	$152.40
Purchase #7	$85.91	8.184%	$92.9409	$92.94	$92.95	$92.90
7 purchase totals =	$1,051.50		$1,134.5464	$1,134.55	$1,134.50	$1,134.50