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	$137.97	5.858%	$146.0523	$146.05	$146.05	$146.10
Purchase #2	$12.36	11.712%	$13.8076	$13.81	$13.80	$13.80
Purchase #3	$93.54	7.579%	$100.6294	$100.63	$100.65	$100.60
Purchase #4	$142.29	6.748%	$151.8917	$151.89	$151.90	$151.90
Purchase #5	$70.45	9.312%	$77.0103	$77.01	$77.00	$77.00
Purchase #6	$5.84	5.223%	$6.145	$6.15	$6.15	$6.10
Purchase #7	$79.65	12.392%	$89.5202	$89.52	$89.50	$89.50
7 purchase totals =	$542.10		$585.0565	$585.06	$585.05	$585.00