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	$142.83	6.819%	$152.5696	$152.57	$152.55	$152.60
Purchase #2	$23.94	8.104%	$25.8801	$25.88	$25.90	$25.90
Purchase #3	$195.40	13.130%	$221.056	$221.06	$221.05	$221.10
Purchase #4	$140.32	13.327%	$159.0204	$159.02	$159.00	$159.00
Purchase #5	$248.90	5.861%	$263.488	$263.49	$263.50	$263.50
Purchase #6	$125.77	10.691%	$139.2161	$139.22	$139.20	$139.20
Purchase #7	$69.62	13.283%	$78.8676	$78.87	$78.85	$78.90
7 purchase totals =	$946.78		$1,040.0978	$1,040.11	$1,040.05	$1,040.20