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	$233.72	4.325%	$243.8284	$243.83	$243.85	$243.80
Purchase #2	$71.28	9.455%	$78.0195	$78.02	$78.00	$78.00
Purchase #3	$115.61	10.139%	$127.3317	$127.33	$127.35	$127.30
Purchase #4	$232.49	6.838%	$248.3877	$248.39	$248.40	$248.40
Purchase #5	$176.33	11.131%	$195.9573	$195.96	$195.95	$196.00
Purchase #6	$133.76	5.869%	$141.6104	$141.61	$141.60	$141.60
Purchase #7	$106.90	3.482%	$110.6223	$110.62	$110.60	$110.60
7 purchase totals =	$1,070.09		$1,145.7573	$1,145.76	$1,145.75	$1,145.70