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	$126.50	13.301%	$143.3258	$143.33	$143.35	$143.30
Purchase #2	$188.42	12.291%	$211.5787	$211.58	$211.60	$211.60
Purchase #3	$214.41	6.809%	$229.0092	$229.01	$229.00	$229.00
Purchase #4	$121.75	10.492%	$134.524	$134.52	$134.50	$134.50
Purchase #5	$240.26	4.111%	$250.1371	$250.14	$250.15	$250.10
Purchase #6	$29.46	5.690%	$31.1363	$31.14	$31.15	$31.10
Purchase #7	$22.61	4.332%	$23.5895	$23.59	$23.60	$23.60
7 purchase totals =	$943.41		$1,023.3006	$1,023.31	$1,023.35	$1,023.20