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	$170.84	10.159%	$188.1956	$188.20	$188.20	$188.20
Purchase #2	$78.46	4.442%	$81.9452	$81.95	$81.95	$81.90
Purchase #3	$145.75	3.373%	$150.6661	$150.67	$150.65	$150.70
Purchase #4	$212.72	11.834%	$237.8933	$237.89	$237.90	$237.90
Purchase #5	$234.48	13.184%	$265.3938	$265.39	$265.40	$265.40
Purchase #6	$95.36	3.508%	$98.7052	$98.71	$98.70	$98.70
Purchase #7	$78.78	9.836%	$86.5288	$86.53	$86.55	$86.50
7 purchase totals =	$1,016.39		$1,109.3280	$1,109.34	$1,109.35	$1,109.30