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	$177.33	10.863%	$196.5934	$196.59	$196.60	$196.60
Purchase #2	$151.33	7.140%	$162.135	$162.14	$162.15	$162.10
Purchase #3	$124.59	5.222%	$131.0961	$131.10	$131.10	$131.10
Purchase #4	$75.31	7.265%	$80.7813	$80.78	$80.80	$80.80
Purchase #5	$191.39	10.376%	$211.2486	$211.25	$211.25	$211.20
Purchase #6	$161.90	6.385%	$172.2373	$172.24	$172.25	$172.20
Purchase #7	$241.85	10.444%	$267.1088	$267.11	$267.10	$267.10
7 purchase totals =	$1,123.70		$1,221.2005	$1,221.21	$1,221.25	$1,221.10