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	$182.88	9.756%	$200.7218	$200.72	$200.70	$200.70
Purchase #2	$162.87	3.575%	$168.6926	$168.69	$168.70	$168.70
Purchase #3	$41.38	3.326%	$42.7563	$42.76	$42.75	$42.80
Purchase #4	$17.54	9.643%	$19.2314	$19.23	$19.25	$19.20
Purchase #5	$19.82	6.786%	$21.165	$21.17	$21.15	$21.20
Purchase #6	$234.96	10.773%	$260.2722	$260.27	$260.25	$260.30
Purchase #7	$53.81	13.556%	$61.1045	$61.10	$61.10	$61.10
7 purchase totals =	$713.26		$773.9438	$773.94	$773.90	$774.00