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	$145.30	5.722%	$153.6141	$153.61	$153.60	$153.60
Purchase #2	$236.33	6.165%	$250.8997	$250.90	$250.90	$250.90
Purchase #3	$35.72	3.187%	$36.8584	$36.86	$36.85	$36.90
Purchase #4	$109.43	9.448%	$119.7689	$119.77	$119.75	$119.80
Purchase #5	$81.45	4.675%	$85.2578	$85.26	$85.25	$85.30
Purchase #6	$163.98	8.608%	$178.0954	$178.10	$178.10	$178.10
Purchase #7	$180.27	6.339%	$191.6973	$191.70	$191.70	$191.70
7 purchase totals =	$952.48		$1,016.1916	$1,016.20	$1,016.15	$1,016.30