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	$184.42	13.798%	$209.8663	$209.87	$209.85	$209.90
Purchase #2	$41.56	9.146%	$45.3611	$45.36	$45.35	$45.40
Purchase #3	$88.27	11.846%	$98.7265	$98.73	$98.75	$98.70
Purchase #4	$172.30	5.816%	$182.321	$182.32	$182.30	$182.30
Purchase #5	$223.51	3.279%	$230.8389	$230.84	$230.85	$230.80
Purchase #6	$42.46	9.696%	$46.5769	$46.58	$46.60	$46.60
Purchase #7	$123.78	10.784%	$137.1284	$137.13	$137.15	$137.10
7 purchase totals =	$876.30		$950.8191	$950.83	$950.85	$950.80