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	$225.78	3.647%	$234.0142	$234.01	$234.00	$234.00
Purchase #2	$229.93	6.809%	$245.5859	$245.59	$245.60	$245.60
Purchase #3	$36.82	4.472%	$38.4666	$38.47	$38.45	$38.50
Purchase #4	$52.28	9.251%	$57.1164	$57.12	$57.10	$57.10
Purchase #5	$5.60	7.767%	$6.035	$6.04	$6.05	$6.00
Purchase #6	$80.30	6.463%	$85.4898	$85.49	$85.50	$85.50
Purchase #7	$66.98	7.818%	$72.2165	$72.22	$72.20	$72.20
7 purchase totals =	$697.69		$738.9244	$738.94	$738.90	$738.90