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	$165.92	5.718%	$175.4073	$175.41	$175.40	$175.40
Purchase #2	$137.77	4.637%	$144.1584	$144.16	$144.15	$144.20
Purchase #3	$207.63	5.778%	$219.6269	$219.63	$219.65	$219.60
Purchase #4	$109.64	10.156%	$120.775	$120.78	$120.80	$120.80
Purchase #5	$119.46	9.770%	$131.1312	$131.13	$131.15	$131.10
Purchase #6	$185.99	12.458%	$209.1606	$209.16	$209.15	$209.20
Purchase #7	$130.54	11.469%	$145.5116	$145.51	$145.50	$145.50
7 purchase totals =	$1,056.95		$1,145.7710	$1,145.78	$1,145.80	$1,145.80