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	$169.77	12.861%	$191.6041	$191.60	$191.60	$191.60
Purchase #2	$168.30	6.750%	$179.6603	$179.66	$179.65	$179.70
Purchase #3	$151.40	3.431%	$156.5945	$156.59	$156.60	$156.60
Purchase #4	$178.48	5.305%	$187.9484	$187.95	$187.95	$187.90
Purchase #5	$96.50	12.556%	$108.6165	$108.62	$108.60	$108.60
Purchase #6	$127.47	11.537%	$142.1762	$142.18	$142.20	$142.20
Purchase #7	$40.31	8.570%	$43.7646	$43.76	$43.75	$43.80
7 purchase totals =	$932.23		$1,010.3646	$1,010.36	$1,010.35	$1,010.40