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	$165.30	5.201%	$173.8973	$173.90	$173.90	$173.90
Purchase #2	$184.52	3.714%	$191.3731	$191.37	$191.35	$191.40
Purchase #3	$177.80	11.689%	$198.583	$198.58	$198.60	$198.60
Purchase #4	$189.27	3.612%	$196.1064	$196.11	$196.10	$196.10
Purchase #5	$109.81	7.801%	$118.3763	$118.38	$118.40	$118.40
Purchase #6	$87.28	4.794%	$91.4642	$91.46	$91.45	$91.50
Purchase #7	$64.47	11.357%	$71.7919	$71.79	$71.80	$71.80
7 purchase totals =	$978.45		$1,041.5922	$1,041.59	$1,041.60	$1,041.70