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	$242.41	8.188%	$262.2585	$262.26	$262.25	$262.30
Purchase #2	$68.92	5.738%	$72.8746	$72.87	$72.85	$72.90
Purchase #3	$204.45	10.360%	$225.631	$225.63	$225.65	$225.60
Purchase #4	$147.80	4.284%	$154.1318	$154.13	$154.15	$154.10
Purchase #5	$74.31	7.790%	$80.0987	$80.10	$80.10	$80.10
Purchase #6	$238.38	10.221%	$262.7448	$262.74	$262.75	$262.70
Purchase #7	$78.78	13.606%	$89.4988	$89.50	$89.50	$89.50
7 purchase totals =	$1,055.05		$1,147.2382	$1,147.23	$1,147.25	$1,147.20