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	$98.83	12.714%	$111.3952	$111.40	$111.40	$111.40
Purchase #2	$135.44	12.208%	$151.9745	$151.97	$151.95	$152.00
Purchase #3	$68.75	13.640%	$78.1275	$78.13	$78.15	$78.10
Purchase #4	$174.64	9.292%	$190.8675	$190.87	$190.85	$190.90
Purchase #5	$250.54	7.616%	$269.6211	$269.62	$269.60	$269.60
Purchase #6	$54.25	4.164%	$56.509	$56.51	$56.50	$56.50
Purchase #7	$175.84	6.625%	$187.4894	$187.49	$187.50	$187.50
7 purchase totals =	$958.29		$1,045.9842	$1,045.99	$1,045.95	$1,046.00