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	$142.45	8.497%	$154.554	$154.55	$154.55	$154.60
Purchase #2	$244.72	4.302%	$255.2479	$255.25	$255.25	$255.20
Purchase #3	$152.42	5.564%	$160.9006	$160.90	$160.90	$160.90
Purchase #4	$96.38	8.766%	$104.8287	$104.83	$104.85	$104.80
Purchase #5	$80.27	13.792%	$91.3408	$91.34	$91.35	$91.30
Purchase #6	$113.44	5.338%	$119.4954	$119.50	$119.50	$119.50
Purchase #7	$184.74	13.292%	$209.2956	$209.30	$209.30	$209.30
7 purchase totals =	$1,014.42		$1,095.6630	$1,095.67	$1,095.70	$1,095.60