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	$224.82	5.650%	$237.5223	$237.52	$237.50	$237.50
Purchase #2	$99.94	9.205%	$109.1395	$109.14	$109.15	$109.10
Purchase #3	$109.56	8.554%	$118.9318	$118.93	$118.95	$118.90
Purchase #4	$154.29	10.438%	$170.3948	$170.39	$170.40	$170.40
Purchase #5	$106.61	6.809%	$113.8691	$113.87	$113.85	$113.90
Purchase #6	$245.89	12.297%	$276.1271	$276.13	$276.15	$276.10
Purchase #7	$73.70	12.817%	$83.1461	$83.15	$83.15	$83.10
7 purchase totals =	$1,014.81		$1,109.1307	$1,109.13	$1,109.15	$1,109.00