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	$17.71	4.804%	$18.5608	$18.56	$18.55	$18.60
Purchase #2	$80.70	6.703%	$86.1093	$86.11	$86.10	$86.10
Purchase #3	$153.27	11.426%	$170.7826	$170.78	$170.80	$170.80
Purchase #4	$139.58	9.338%	$152.614	$152.61	$152.60	$152.60
Purchase #5	$31.66	3.482%	$32.7624	$32.76	$32.75	$32.80
Purchase #6	$100.85	4.548%	$105.4367	$105.44	$105.45	$105.40
Purchase #7	$137.45	7.415%	$147.6419	$147.64	$147.65	$147.60
7 purchase totals =	$661.22		$713.9077	$713.90	$713.90	$713.90