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	$134.74	5.647%	$142.3488	$142.35	$142.35	$142.30
Purchase #2	$144.37	6.656%	$153.9793	$153.98	$154.00	$154.00
Purchase #3	$171.63	10.283%	$189.2787	$189.28	$189.30	$189.30
Purchase #4	$80.81	11.545%	$90.1395	$90.14	$90.15	$90.10
Purchase #5	$165.71	3.297%	$171.1735	$171.17	$171.15	$171.20
Purchase #6	$111.44	11.190%	$123.9101	$123.91	$123.90	$123.90
Purchase #7	$69.55	10.291%	$76.7074	$76.71	$76.70	$76.70
7 purchase totals =	$878.25		$947.5373	$947.54	$947.55	$947.50