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	$100.90	6.435%	$107.3929	$107.39	$107.40	$107.40
Purchase #2	$154.38	6.432%	$164.3097	$164.31	$164.30	$164.30
Purchase #3	$41.79	3.604%	$43.2961	$43.30	$43.30	$43.30
Purchase #4	$235.39	5.596%	$248.5624	$248.56	$248.55	$248.60
Purchase #5	$68.76	13.565%	$78.0873	$78.09	$78.10	$78.10
Purchase #6	$148.89	5.118%	$156.5102	$156.51	$156.50	$156.50
Purchase #7	$57.98	6.452%	$61.7209	$61.72	$61.70	$61.70
7 purchase totals =	$808.09		$859.8795	$859.88	$859.85	$859.90