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	$185.69	3.143%	$191.5262	$191.53	$191.55	$191.50
Purchase #2	$167.83	10.580%	$185.5864	$185.59	$185.60	$185.60
Purchase #3	$97.63	5.398%	$102.9001	$102.90	$102.90	$102.90
Purchase #4	$119.46	4.373%	$124.684	$124.68	$124.70	$124.70
Purchase #5	$178.40	5.267%	$187.7963	$187.80	$187.80	$187.80
Purchase #6	$39.71	6.593%	$42.3281	$42.33	$42.35	$42.30
Purchase #7	$68.70	12.469%	$77.2662	$77.27	$77.25	$77.30
7 purchase totals =	$857.42		$912.0873	$912.10	$912.15	$912.10