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	$123.79	7.733%	$133.3627	$133.36	$133.35	$133.40
Purchase #2	$83.93	12.311%	$94.2626	$94.26	$94.25	$94.30
Purchase #3	$79.31	5.354%	$83.5563	$83.56	$83.55	$83.60
Purchase #4	$195.59	13.560%	$222.112	$222.11	$222.10	$222.10
Purchase #5	$58.51	11.228%	$65.0795	$65.08	$65.10	$65.10
Purchase #6	$214.39	11.195%	$238.391	$238.39	$238.40	$238.40
Purchase #7	$203.32	11.833%	$227.3789	$227.38	$227.40	$227.40
7 purchase totals =	$958.84		$1,064.1430	$1,064.14	$1,064.15	$1,064.30