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	$190.54	10.799%	$211.1164	$211.12	$211.10	$211.10
Purchase #2	$57.70	4.390%	$60.233	$60.23	$60.25	$60.20
Purchase #3	$78.30	10.742%	$86.711	$86.71	$86.70	$86.70
Purchase #4	$196.50	12.127%	$220.3296	$220.33	$220.35	$220.30
Purchase #5	$35.83	7.239%	$38.4237	$38.42	$38.40	$38.40
Purchase #6	$89.84	10.807%	$99.549	$99.55	$99.55	$99.50
Purchase #7	$21.51	4.484%	$22.4745	$22.47	$22.45	$22.50
7 purchase totals =	$670.22		$738.8372	$738.83	$738.80	$738.70