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	$104.79	10.642%	$115.9418	$115.94	$115.95	$115.90
Purchase #2	$54.89	11.304%	$61.0948	$61.09	$61.10	$61.10
Purchase #3	$233.98	9.382%	$255.932	$255.93	$255.95	$255.90
Purchase #4	$179.76	3.211%	$185.5321	$185.53	$185.55	$185.50
Purchase #5	$151.88	5.736%	$160.5918	$160.59	$160.60	$160.60
Purchase #6	$129.91	5.572%	$137.1486	$137.15	$137.15	$137.10
Purchase #7	$229.76	7.130%	$246.1419	$246.14	$246.15	$246.10
7 purchase totals =	$1,084.97		$1,162.3830	$1,162.37	$1,162.45	$1,162.20