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	$199.51	11.506%	$222.4656	$222.47	$222.45	$222.50
Purchase #2	$187.48	13.455%	$212.7054	$212.71	$212.70	$212.70
Purchase #3	$181.84	9.459%	$199.0402	$199.04	$199.05	$199.00
Purchase #4	$81.38	5.563%	$85.9072	$85.91	$85.90	$85.90
Purchase #5	$209.90	9.380%	$229.5886	$229.59	$229.60	$229.60
Purchase #6	$49.27	9.398%	$53.9004	$53.90	$53.90	$53.90
Purchase #7	$78.85	10.168%	$86.8675	$86.87	$86.85	$86.90
7 purchase totals =	$988.23		$1,090.4749	$1,090.49	$1,090.45	$1,090.50