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	$189.45	10.212%	$208.7966	$208.80	$208.80	$208.80
Purchase #2	$70.79	11.414%	$78.87	$78.87	$78.85	$78.90
Purchase #3	$51.84	7.172%	$55.558	$55.56	$55.55	$55.60
Purchase #4	$57.65	6.251%	$61.2537	$61.25	$61.25	$61.30
Purchase #5	$73.97	9.350%	$80.8862	$80.89	$80.90	$80.90
Purchase #6	$66.39	4.730%	$69.5302	$69.53	$69.55	$69.50
Purchase #7	$234.45	3.435%	$242.5034	$242.50	$242.50	$242.50
7 purchase totals =	$744.54		$797.3981	$797.40	$797.40	$797.50