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	$76.62	12.559%	$86.2427	$86.24	$86.25	$86.20
Purchase #2	$93.86	12.635%	$105.7192	$105.72	$105.70	$105.70
Purchase #3	$99.87	13.558%	$113.4104	$113.41	$113.40	$113.40
Purchase #4	$42.96	5.439%	$45.2966	$45.30	$45.30	$45.30
Purchase #5	$116.52	8.647%	$126.5955	$126.60	$126.60	$126.60
Purchase #6	$102.29	5.148%	$107.5559	$107.56	$107.55	$107.60
Purchase #7	$94.36	12.233%	$105.9031	$105.90	$105.90	$105.90
7 purchase totals =	$626.48		$690.7234	$690.73	$690.70	$690.70