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	$134.40	7.760%	$144.8294	$144.83	$144.85	$144.80
Purchase #2	$96.89	8.862%	$105.4764	$105.48	$105.50	$105.50
Purchase #3	$36.48	6.429%	$38.8253	$38.83	$38.85	$38.80
Purchase #4	$77.87	5.525%	$82.1723	$82.17	$82.15	$82.20
Purchase #5	$206.89	4.425%	$216.0449	$216.04	$216.05	$216.00
Purchase #6	$181.36	3.123%	$187.0239	$187.02	$187.00	$187.00
Purchase #7	$91.99	3.459%	$95.1719	$95.17	$95.15	$95.20
7 purchase totals =	$825.88		$869.5441	$869.54	$869.55	$869.50