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	$199.27	8.850%	$216.9054	$216.91	$216.90	$216.90
Purchase #2	$103.88	4.348%	$108.3967	$108.40	$108.40	$108.40
Purchase #3	$86.44	5.793%	$91.4475	$91.45	$91.45	$91.40
Purchase #4	$79.86	4.304%	$83.2972	$83.30	$83.30	$83.30
Purchase #5	$105.48	13.154%	$119.3548	$119.35	$119.35	$119.40
Purchase #6	$119.71	6.643%	$127.6623	$127.66	$127.65	$127.70
Purchase #7	$202.52	7.824%	$218.3652	$218.37	$218.35	$218.40
7 purchase totals =	$897.16		$965.4291	$965.44	$965.40	$965.50