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	$208.45	5.523%	$219.9627	$219.96	$219.95	$220.00
Purchase #2	$165.56	9.201%	$180.7932	$180.79	$180.80	$180.80
Purchase #3	$133.45	7.107%	$142.9343	$142.93	$142.95	$142.90
Purchase #4	$61.91	5.714%	$65.4475	$65.45	$65.45	$65.40
Purchase #5	$137.44	7.609%	$147.8978	$147.90	$147.90	$147.90
Purchase #6	$80.62	6.133%	$85.5644	$85.56	$85.55	$85.60
Purchase #7	$147.95	9.540%	$162.0644	$162.06	$162.05	$162.10
7 purchase totals =	$935.38		$1,004.6643	$1,004.65	$1,004.65	$1,004.70