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	$76.81	11.794%	$85.869	$85.87	$85.85	$85.90
Purchase #2	$165.49	3.773%	$171.7339	$171.73	$171.75	$171.70
Purchase #3	$110.59	12.664%	$124.5951	$124.60	$124.60	$124.60
Purchase #4	$101.87	5.631%	$107.6063	$107.61	$107.60	$107.60
Purchase #5	$210.33	5.846%	$222.6259	$222.63	$222.65	$222.60
Purchase #6	$38.83	10.746%	$43.0027	$43.00	$43.00	$43.00
Purchase #7	$214.52	3.621%	$222.2878	$222.29	$222.30	$222.30
7 purchase totals =	$918.44		$977.7207	$977.73	$977.75	$977.70