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	$120.92	4.834%	$126.7653	$126.77	$126.75	$126.80
Purchase #2	$148.39	9.349%	$162.263	$162.26	$162.25	$162.30
Purchase #3	$174.53	6.552%	$185.9652	$185.97	$185.95	$186.00
Purchase #4	$180.37	3.466%	$186.6216	$186.62	$186.60	$186.60
Purchase #5	$194.73	10.712%	$215.5895	$215.59	$215.60	$215.60
Purchase #6	$117.43	8.559%	$127.4808	$127.48	$127.50	$127.50
Purchase #7	$109.96	3.152%	$113.4259	$113.43	$113.45	$113.40
7 purchase totals =	$1,046.33		$1,118.1113	$1,118.12	$1,118.10	$1,118.20