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	$163.61	4.713%	$171.3209	$171.32	$171.30	$171.30
Purchase #2	$55.73	7.300%	$59.7983	$59.80	$59.80	$59.80
Purchase #3	$96.29	5.700%	$101.7785	$101.78	$101.80	$101.80
Purchase #4	$44.25	3.147%	$45.6425	$45.64	$45.65	$45.60
Purchase #5	$227.79	3.529%	$235.8287	$235.83	$235.85	$235.80
Purchase #6	$166.67	13.159%	$188.6021	$188.60	$188.60	$188.60
Purchase #7	$178.81	13.541%	$203.0227	$203.02	$203.00	$203.00
7 purchase totals =	$933.15		$1,005.9937	$1,005.99	$1,006.00	$1,005.90