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	$96.25	4.357%	$100.4436	$100.44	$100.45	$100.40
Purchase #2	$36.73	11.668%	$41.0157	$41.02	$41.00	$41.00
Purchase #3	$88.79	10.867%	$98.4388	$98.44	$98.45	$98.40
Purchase #4	$84.32	3.513%	$87.2822	$87.28	$87.30	$87.30
Purchase #5	$78.96	11.865%	$88.3286	$88.33	$88.35	$88.30
Purchase #6	$95.52	5.621%	$100.8892	$100.89	$100.90	$100.90
Purchase #7	$198.44	8.797%	$215.8968	$215.90	$215.90	$215.90
7 purchase totals =	$679.01		$732.2949	$732.30	$732.35	$732.20