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	$171.69	7.720%	$184.9445	$184.94	$184.95	$184.90
Purchase #2	$6.44	12.630%	$7.2534	$7.25	$7.25	$7.30
Purchase #3	$48.32	10.323%	$53.3081	$53.31	$53.30	$53.30
Purchase #4	$162.36	3.837%	$168.5898	$168.59	$168.60	$168.60
Purchase #5	$83.84	6.235%	$89.0674	$89.07	$89.05	$89.10
Purchase #6	$75.97	7.132%	$81.3882	$81.39	$81.40	$81.40
Purchase #7	$19.73	3.440%	$20.4087	$20.41	$20.40	$20.40
7 purchase totals =	$568.35		$604.9601	$604.96	$604.95	$605.00