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	$102.83	9.634%	$112.7366	$112.74	$112.75	$112.70
Purchase #2	$199.67	9.773%	$219.1837	$219.18	$219.20	$219.20
Purchase #3	$164.85	13.288%	$186.7553	$186.76	$186.75	$186.80
Purchase #4	$239.93	13.494%	$272.3062	$272.31	$272.30	$272.30
Purchase #5	$96.42	8.364%	$104.4846	$104.48	$104.50	$104.50
Purchase #6	$115.76	9.835%	$127.145	$127.15	$127.15	$127.10
Purchase #7	$88.43	7.263%	$94.8527	$94.85	$94.85	$94.90
7 purchase totals =	$1,007.89		$1,117.4641	$1,117.47	$1,117.50	$1,117.50