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	$103.72	9.166%	$113.227	$113.23	$113.25	$113.20
Purchase #2	$35.96	7.445%	$38.6372	$38.64	$38.65	$38.60
Purchase #3	$45.47	8.524%	$49.3459	$49.35	$49.35	$49.30
Purchase #4	$47.33	11.295%	$52.6759	$52.68	$52.70	$52.70
Purchase #5	$111.36	11.221%	$123.8557	$123.86	$123.85	$123.90
Purchase #6	$143.35	10.461%	$158.3458	$158.35	$158.35	$158.30
Purchase #7	$174.79	6.591%	$186.3104	$186.31	$186.30	$186.30
7 purchase totals =	$661.98		$722.3979	$722.42	$722.45	$722.30