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	$118.46	10.727%	$131.1672	$131.17	$131.15	$131.20
Purchase #2	$230.51	3.444%	$238.4488	$238.45	$238.45	$238.40
Purchase #3	$48.46	11.179%	$53.8773	$53.88	$53.90	$53.90
Purchase #4	$211.46	13.246%	$239.47	$239.47	$239.45	$239.50
Purchase #5	$78.27	4.742%	$81.9816	$81.98	$82.00	$82.00
Purchase #6	$72.54	3.278%	$74.9179	$74.92	$74.90	$74.90
Purchase #7	$184.85	10.355%	$203.9912	$203.99	$204.00	$204.00
7 purchase totals =	$944.55		$1,023.8540	$1,023.86	$1,023.85	$1,023.90