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	$25.68	4.587%	$26.8579	$26.86	$26.85	$26.90
Purchase #2	$196.43	7.837%	$211.8242	$211.82	$211.80	$211.80
Purchase #3	$171.32	8.360%	$185.6424	$185.64	$185.65	$185.60
Purchase #4	$96.28	4.341%	$100.4595	$100.46	$100.45	$100.50
Purchase #5	$102.83	10.155%	$113.2724	$113.27	$113.25	$113.30
Purchase #6	$222.28	8.489%	$241.1493	$241.15	$241.15	$241.10
Purchase #7	$241.66	10.789%	$267.7327	$267.73	$267.75	$267.70
7 purchase totals =	$1,056.48		$1,146.9384	$1,146.93	$1,146.90	$1,146.90