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	$112.43	3.822%	$116.7271	$116.73	$116.75	$116.70
Purchase #2	$29.39	4.809%	$30.8034	$30.80	$30.80	$30.80
Purchase #3	$143.66	4.638%	$150.323	$150.32	$150.30	$150.30
Purchase #4	$35.83	13.657%	$40.7233	$40.72	$40.70	$40.70
Purchase #5	$163.79	4.547%	$171.2375	$171.24	$171.25	$171.20
Purchase #6	$96.91	3.799%	$100.5916	$100.59	$100.60	$100.60
Purchase #7	$74.40	4.360%	$77.6438	$77.64	$77.65	$77.60
7 purchase totals =	$656.41		$688.0497	$688.04	$688.05	$687.90