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	$92.33	4.399%	$96.3916	$96.39	$96.40	$96.40
Purchase #2	$197.80	9.508%	$216.6068	$216.61	$216.60	$216.60
Purchase #3	$33.76	13.278%	$38.2427	$38.24	$38.25	$38.20
Purchase #4	$109.67	12.391%	$123.2592	$123.26	$123.25	$123.30
Purchase #5	$216.91	8.616%	$235.599	$235.60	$235.60	$235.60
Purchase #6	$170.71	10.373%	$188.4177	$188.42	$188.40	$188.40
Purchase #7	$77.63	7.538%	$83.4817	$83.48	$83.50	$83.50
7 purchase totals =	$898.81		$981.9987	$982.00	$982.00	$982.00