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	$63.72	12.406%	$71.6251	$71.63	$71.65	$71.60
Purchase #2	$76.89	6.794%	$82.1139	$82.11	$82.10	$82.10
Purchase #3	$191.60	12.598%	$215.7378	$215.74	$215.75	$215.70
Purchase #4	$54.25	10.111%	$59.7352	$59.74	$59.75	$59.70
Purchase #5	$217.56	8.263%	$235.537	$235.54	$235.55	$235.50
Purchase #6	$250.71	12.697%	$282.5426	$282.54	$282.55	$282.50
Purchase #7	$150.94	10.596%	$166.9336	$166.93	$166.95	$166.90
7 purchase totals =	$1,005.67		$1,114.2252	$1,114.23	$1,114.30	$1,114.00