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	$59.56	5.282%	$62.706	$62.71	$62.70	$62.70
Purchase #2	$100.87	8.584%	$109.5287	$109.53	$109.55	$109.50
Purchase #3	$148.86	10.575%	$164.6019	$164.60	$164.60	$164.60
Purchase #4	$249.46	8.360%	$270.3149	$270.31	$270.30	$270.30
Purchase #5	$246.99	9.174%	$269.6489	$269.65	$269.65	$269.60
Purchase #6	$143.86	6.561%	$153.2987	$153.30	$153.30	$153.30
Purchase #7	$73.67	13.833%	$83.8608	$83.86	$83.85	$83.90
7 purchase totals =	$1,023.27		$1,113.9599	$1,113.96	$1,113.95	$1,113.90