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	$176.80	5.125%	$185.861	$185.86	$185.85	$185.90
Purchase #2	$191.27	3.624%	$198.2016	$198.20	$198.20	$198.20
Purchase #3	$154.74	9.686%	$169.7281	$169.73	$169.75	$169.70
Purchase #4	$112.37	5.412%	$118.4515	$118.45	$118.45	$118.50
Purchase #5	$166.45	5.620%	$175.8045	$175.80	$175.80	$175.80
Purchase #6	$160.53	12.404%	$180.4421	$180.44	$180.45	$180.40
Purchase #7	$50.50	13.851%	$57.4948	$57.49	$57.50	$57.50
7 purchase totals =	$1,012.66		$1,085.9836	$1,085.97	$1,086.00	$1,086.00