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	$193.74	3.170%	$199.8816	$199.88	$199.90	$199.90
Purchase #2	$122.97	5.287%	$129.4714	$129.47	$129.45	$129.50
Purchase #3	$165.89	5.114%	$174.3736	$174.37	$174.35	$174.40
Purchase #4	$237.93	9.435%	$260.3787	$260.38	$260.40	$260.40
Purchase #5	$243.41	6.145%	$258.3675	$258.37	$258.35	$258.40
Purchase #6	$73.31	12.659%	$82.5903	$82.59	$82.60	$82.60
Purchase #7	$38.34	3.738%	$39.7731	$39.77	$39.75	$39.80
7 purchase totals =	$1,075.59		$1,144.8362	$1,144.83	$1,144.80	$1,145.00