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	$110.73	5.247%	$116.54	$116.54	$116.55	$116.50
Purchase #2	$6.82	6.808%	$7.2843	$7.28	$7.30	$7.30
Purchase #3	$166.80	13.690%	$189.6349	$189.63	$189.65	$189.60
Purchase #4	$35.44	13.311%	$40.1574	$40.16	$40.15	$40.20
Purchase #5	$133.58	8.385%	$144.7807	$144.78	$144.80	$144.80
Purchase #6	$112.34	10.287%	$123.8964	$123.90	$123.90	$123.90
Purchase #7	$100.61	5.107%	$105.7482	$105.75	$105.75	$105.70
7 purchase totals =	$666.32		$728.0419	$728.04	$728.10	$728.00