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	$104.65	3.859%	$108.6884	$108.69	$108.70	$108.70
Purchase #2	$188.59	8.870%	$205.3179	$205.32	$205.30	$205.30
Purchase #3	$6.82	9.709%	$7.4822	$7.48	$7.50	$7.50
Purchase #4	$140.75	8.589%	$152.839	$152.84	$152.85	$152.80
Purchase #5	$171.80	9.597%	$188.2876	$188.29	$188.30	$188.30
Purchase #6	$42.40	4.329%	$44.2355	$44.24	$44.25	$44.20
Purchase #7	$150.32	9.551%	$164.6771	$164.68	$164.70	$164.70
7 purchase totals =	$805.33		$871.5277	$871.54	$871.60	$871.50