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	$96.46	3.618%	$99.9499	$99.95	$99.95	$99.90
Purchase #2	$103.99	10.471%	$114.8788	$114.88	$114.90	$114.90
Purchase #3	$228.50	8.342%	$247.5615	$247.56	$247.55	$247.60
Purchase #4	$133.47	3.423%	$138.0387	$138.04	$138.05	$138.00
Purchase #5	$245.41	12.242%	$275.4531	$275.45	$275.45	$275.50
Purchase #6	$33.59	12.460%	$37.7753	$37.78	$37.80	$37.80
Purchase #7	$239.94	6.757%	$256.1527	$256.15	$256.15	$256.20
7 purchase totals =	$1,081.36		$1,169.8100	$1,169.81	$1,169.85	$1,169.90