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	$84.59	7.870%	$91.2472	$91.25	$91.25	$91.20
Purchase #2	$131.73	12.477%	$148.166	$148.17	$148.15	$148.20
Purchase #3	$107.26	11.174%	$119.2452	$119.25	$119.25	$119.20
Purchase #4	$187.60	6.644%	$200.0641	$200.06	$200.05	$200.10
Purchase #5	$186.36	13.175%	$210.9129	$210.91	$210.90	$210.90
Purchase #6	$210.72	11.412%	$234.7674	$234.77	$234.75	$234.80
Purchase #7	$39.59	9.385%	$43.3055	$43.31	$43.30	$43.30
7 purchase totals =	$947.85		$1,047.7083	$1,047.72	$1,047.65	$1,047.70