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	$243.33	10.824%	$269.668	$269.67	$269.65	$269.70
Purchase #2	$110.35	8.342%	$119.5554	$119.56	$119.55	$119.60
Purchase #3	$104.96	11.791%	$117.3358	$117.34	$117.35	$117.30
Purchase #4	$72.33	3.372%	$74.769	$74.77	$74.75	$74.80
Purchase #5	$16.56	3.118%	$17.0763	$17.08	$17.10	$17.10
Purchase #6	$91.50	9.844%	$100.5073	$100.51	$100.50	$100.50
Purchase #7	$55.61	6.368%	$59.1512	$59.15	$59.15	$59.20
7 purchase totals =	$694.64		$758.0630	$758.08	$758.05	$758.20