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	$211.41	5.247%	$222.5027	$222.50	$222.50	$222.50
Purchase #2	$124.85	13.594%	$141.8221	$141.82	$141.80	$141.80
Purchase #3	$142.88	10.152%	$157.3852	$157.39	$157.40	$157.40
Purchase #4	$67.42	13.519%	$76.5345	$76.53	$76.55	$76.50
Purchase #5	$139.40	11.133%	$154.9194	$154.92	$154.90	$154.90
Purchase #6	$210.64	3.755%	$218.5495	$218.55	$218.55	$218.50
Purchase #7	$211.49	4.427%	$220.8527	$220.85	$220.85	$220.90
7 purchase totals =	$1,108.09		$1,192.5661	$1,192.56	$1,192.55	$1,192.50