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	$171.47	6.652%	$182.8762	$182.88	$182.90	$182.90
Purchase #2	$214.80	8.774%	$233.6466	$233.65	$233.65	$233.60
Purchase #3	$147.63	12.156%	$165.5759	$165.58	$165.60	$165.60
Purchase #4	$109.66	6.323%	$116.5938	$116.59	$116.60	$116.60
Purchase #5	$180.94	8.697%	$196.6764	$196.68	$196.70	$196.70
Purchase #6	$60.89	7.753%	$65.6108	$65.61	$65.60	$65.60
Purchase #7	$61.30	12.269%	$68.8209	$68.82	$68.80	$68.80
7 purchase totals =	$946.69		$1,029.8006	$1,029.81	$1,029.85	$1,029.80