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	$130.50	11.348%	$145.3091	$145.31	$145.30	$145.30
Purchase #2	$115.89	9.663%	$127.0885	$127.09	$127.10	$127.10
Purchase #3	$113.36	9.401%	$124.017	$124.02	$124.00	$124.00
Purchase #4	$229.43	12.188%	$257.3929	$257.39	$257.40	$257.40
Purchase #5	$150.70	13.683%	$171.3203	$171.32	$171.30	$171.30
Purchase #6	$6.32	6.308%	$6.7187	$6.72	$6.70	$6.70
Purchase #7	$178.66	6.371%	$190.0424	$190.04	$190.05	$190.00
7 purchase totals =	$924.86		$1,021.8889	$1,021.89	$1,021.85	$1,021.80