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	$154.39	8.657%	$167.7555	$167.76	$167.75	$167.80
Purchase #2	$234.74	9.398%	$256.8009	$256.80	$256.80	$256.80
Purchase #3	$130.42	8.529%	$141.5435	$141.54	$141.55	$141.50
Purchase #4	$152.30	6.505%	$162.2071	$162.21	$162.20	$162.20
Purchase #5	$197.30	10.135%	$217.2964	$217.30	$217.30	$217.30
Purchase #6	$73.40	7.431%	$78.8544	$78.85	$78.85	$78.90
Purchase #7	$131.62	9.763%	$144.4701	$144.47	$144.45	$144.50
7 purchase totals =	$1,074.17		$1,168.9279	$1,168.93	$1,168.90	$1,169.00