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	$202.30	6.357%	$215.1602	$215.16	$215.15	$215.20
Purchase #2	$197.26	10.550%	$218.0709	$218.07	$218.05	$218.10
Purchase #3	$244.54	7.459%	$262.7802	$262.78	$262.80	$262.80
Purchase #4	$41.37	10.391%	$45.6688	$45.67	$45.65	$45.70
Purchase #5	$136.68	11.469%	$152.3558	$152.36	$152.35	$152.40
Purchase #6	$99.53	5.726%	$105.2291	$105.23	$105.25	$105.20
Purchase #7	$77.93	11.463%	$86.8631	$86.86	$86.85	$86.90
7 purchase totals =	$999.61		$1,086.1281	$1,086.13	$1,086.10	$1,086.30