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	$240.38	4.782%	$251.875	$251.88	$251.90	$251.90
Purchase #2	$168.55	6.183%	$178.9714	$178.97	$178.95	$179.00
Purchase #3	$113.47	7.245%	$121.6909	$121.69	$121.70	$121.70
Purchase #4	$224.58	8.426%	$243.5031	$243.50	$243.50	$243.50
Purchase #5	$12.37	6.266%	$13.1451	$13.15	$13.15	$13.10
Purchase #6	$188.36	6.662%	$200.9085	$200.91	$200.90	$200.90
Purchase #7	$134.31	13.473%	$152.4056	$152.41	$152.40	$152.40
7 purchase totals =	$1,082.02		$1,162.4996	$1,162.51	$1,162.50	$1,162.50