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	$170.51	7.268%	$182.9027	$182.90	$182.90	$182.90
Purchase #2	$134.63	4.118%	$140.1741	$140.17	$140.15	$140.20
Purchase #3	$100.53	6.545%	$107.1097	$107.11	$107.10	$107.10
Purchase #4	$85.67	5.449%	$90.3382	$90.34	$90.35	$90.30
Purchase #5	$229.95	3.756%	$238.5869	$238.59	$238.60	$238.60
Purchase #6	$160.98	12.193%	$180.6083	$180.61	$180.60	$180.60
Purchase #7	$73.35	4.124%	$76.375	$76.38	$76.40	$76.40
7 purchase totals =	$955.62		$1,016.0949	$1,016.10	$1,016.10	$1,016.10