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	$198.43	8.380%	$215.0584	$215.06	$215.05	$215.10
Purchase #2	$146.70	7.829%	$158.1851	$158.19	$158.20	$158.20
Purchase #3	$57.32	13.669%	$65.1551	$65.16	$65.15	$65.20
Purchase #4	$244.45	5.280%	$257.357	$257.36	$257.35	$257.40
Purchase #5	$225.59	11.126%	$250.6891	$250.69	$250.70	$250.70
Purchase #6	$10.46	4.414%	$10.9217	$10.92	$10.90	$10.90
Purchase #7	$52.56	12.835%	$59.3061	$59.31	$59.30	$59.30
7 purchase totals =	$935.51		$1,016.6725	$1,016.69	$1,016.65	$1,016.80