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	$51.61	5.573%	$54.4862	$54.49	$54.50	$54.50
Purchase #2	$65.27	6.793%	$69.7038	$69.70	$69.70	$69.70
Purchase #3	$204.45	5.494%	$215.6825	$215.68	$215.70	$215.70
Purchase #4	$218.67	3.124%	$225.5013	$225.50	$225.50	$225.50
Purchase #5	$234.96	11.284%	$261.4729	$261.47	$261.45	$261.50
Purchase #6	$55.61	3.473%	$57.5413	$57.54	$57.55	$57.50
Purchase #7	$137.50	6.292%	$146.1515	$146.15	$146.15	$146.20
7 purchase totals =	$968.07		$1,030.5395	$1,030.53	$1,030.55	$1,030.60