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	$181.52	5.714%	$191.8921	$191.89	$191.90	$191.90
Purchase #2	$198.44	5.756%	$209.8622	$209.86	$209.85	$209.90
Purchase #3	$55.90	6.796%	$59.699	$59.70	$59.70	$59.70
Purchase #4	$248.61	8.860%	$270.6368	$270.64	$270.65	$270.60
Purchase #5	$181.37	9.259%	$198.163	$198.16	$198.15	$198.20
Purchase #6	$160.54	11.211%	$178.5381	$178.54	$178.55	$178.50
Purchase #7	$140.40	12.219%	$157.5555	$157.56	$157.55	$157.60
7 purchase totals =	$1,166.78		$1,266.3467	$1,266.35	$1,266.35	$1,266.40