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	$99.96	11.439%	$111.3944	$111.39	$111.40	$111.40
Purchase #2	$43.85	5.355%	$46.1982	$46.20	$46.20	$46.20
Purchase #3	$162.43	13.158%	$183.8025	$183.80	$183.80	$183.80
Purchase #4	$155.56	12.282%	$174.6659	$174.67	$174.65	$174.70
Purchase #5	$106.29	3.111%	$109.5967	$109.60	$109.60	$109.60
Purchase #6	$61.75	7.716%	$66.5146	$66.51	$66.50	$66.50
Purchase #7	$18.69	11.760%	$20.8879	$20.89	$20.90	$20.90
7 purchase totals =	$648.53		$713.0602	$713.06	$713.05	$713.10