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	$197.94	6.739%	$211.2792	$211.28	$211.30	$211.30
Purchase #2	$235.77	6.282%	$250.5811	$250.58	$250.60	$250.60
Purchase #3	$96.79	7.156%	$103.7163	$103.72	$103.70	$103.70
Purchase #4	$241.72	3.131%	$249.2883	$249.29	$249.30	$249.30
Purchase #5	$102.53	13.410%	$116.2793	$116.28	$116.30	$116.30
Purchase #6	$191.97	4.558%	$200.72	$200.72	$200.70	$200.70
Purchase #7	$57.49	12.333%	$64.5802	$64.58	$64.60	$64.60
7 purchase totals =	$1,124.21		$1,196.4444	$1,196.45	$1,196.50	$1,196.50