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	$161.75	4.111%	$168.3995	$168.40	$168.40	$168.40
Purchase #2	$6.89	13.435%	$7.8157	$7.82	$7.80	$7.80
Purchase #3	$163.70	4.825%	$171.5985	$171.60	$171.60	$171.60
Purchase #4	$183.30	7.609%	$197.2473	$197.25	$197.25	$197.20
Purchase #5	$92.37	13.173%	$104.5379	$104.54	$104.55	$104.50
Purchase #6	$101.40	3.870%	$105.3242	$105.32	$105.30	$105.30
Purchase #7	$127.80	13.275%	$144.7655	$144.77	$144.75	$144.80
7 purchase totals =	$837.21		$899.6886	$899.70	$899.65	$899.60