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	$67.72	6.861%	$72.3663	$72.37	$72.35	$72.40
Purchase #2	$181.55	13.469%	$206.003	$206.00	$206.00	$206.00
Purchase #3	$55.34	7.521%	$59.5021	$59.50	$59.50	$59.50
Purchase #4	$167.81	6.571%	$178.8368	$178.84	$178.85	$178.80
Purchase #5	$152.90	10.263%	$168.5921	$168.59	$168.60	$168.60
Purchase #6	$50.77	10.799%	$56.2527	$56.25	$56.25	$56.30
Purchase #7	$205.68	3.470%	$212.8171	$212.82	$212.80	$212.80
7 purchase totals =	$881.77		$954.3701	$954.37	$954.35	$954.40