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	$248.80	8.302%	$269.4554	$269.46	$269.45	$269.50
Purchase #2	$146.57	3.788%	$152.1221	$152.12	$152.10	$152.10
Purchase #3	$110.42	8.191%	$119.4645	$119.46	$119.45	$119.50
Purchase #4	$189.79	10.206%	$209.16	$209.16	$209.15	$209.20
Purchase #5	$117.38	12.219%	$131.7227	$131.72	$131.70	$131.70
Purchase #6	$181.73	11.711%	$203.0124	$203.01	$203.00	$203.00
Purchase #7	$62.90	13.814%	$71.589	$71.59	$71.60	$71.60
7 purchase totals =	$1,057.59		$1,156.5261	$1,156.52	$1,156.45	$1,156.60