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	$96.43	8.163%	$104.3016	$104.30	$104.30	$104.30
Purchase #2	$230.41	7.436%	$247.5433	$247.54	$247.55	$247.50
Purchase #3	$37.76	12.821%	$42.6012	$42.60	$42.60	$42.60
Purchase #4	$151.57	10.256%	$167.115	$167.12	$167.10	$167.10
Purchase #5	$131.65	8.274%	$142.5427	$142.54	$142.55	$142.50
Purchase #6	$168.59	4.416%	$176.0349	$176.03	$176.05	$176.00
Purchase #7	$174.73	9.568%	$191.4482	$191.45	$191.45	$191.40
7 purchase totals =	$991.14		$1,071.5869	$1,071.58	$1,071.60	$1,071.40