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	$14.26	4.316%	$14.8755	$14.88	$14.90	$14.90
Purchase #2	$175.57	13.502%	$199.2755	$199.28	$199.30	$199.30
Purchase #3	$74.71	4.752%	$78.2602	$78.26	$78.25	$78.30
Purchase #4	$90.55	5.154%	$95.2169	$95.22	$95.20	$95.20
Purchase #5	$236.30	13.654%	$268.5644	$268.56	$268.55	$268.60
Purchase #6	$199.84	7.863%	$215.5534	$215.55	$215.55	$215.60
Purchase #7	$213.81	9.119%	$233.3073	$233.31	$233.30	$233.30
7 purchase totals =	$1,005.04		$1,105.0532	$1,105.06	$1,105.05	$1,105.20