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	$177.92	9.300%	$194.4666	$194.47	$194.45	$194.50
Purchase #2	$185.37	6.141%	$196.7536	$196.75	$196.75	$196.80
Purchase #3	$218.48	11.431%	$243.4544	$243.45	$243.45	$243.50
Purchase #4	$133.47	5.541%	$140.8656	$140.87	$140.85	$140.90
Purchase #5	$31.46	10.765%	$34.8467	$34.85	$34.85	$34.80
Purchase #6	$83.36	5.721%	$88.129	$88.13	$88.15	$88.10
Purchase #7	$200.87	7.160%	$215.2523	$215.25	$215.25	$215.30
7 purchase totals =	$1,030.93		$1,113.7682	$1,113.77	$1,113.75	$1,113.90