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	$51.76	3.133%	$53.3816	$53.38	$53.40	$53.40
Purchase #2	$242.62	4.578%	$253.7271	$253.73	$253.75	$253.70
Purchase #3	$159.50	3.808%	$165.5738	$165.57	$165.55	$165.60
Purchase #4	$206.89	6.853%	$221.0682	$221.07	$221.05	$221.10
Purchase #5	$81.33	9.529%	$89.0799	$89.08	$89.10	$89.10
Purchase #6	$192.95	11.475%	$215.091	$215.09	$215.10	$215.10
Purchase #7	$200.54	11.745%	$224.0934	$224.09	$224.10	$224.10
7 purchase totals =	$1,135.59		$1,222.0150	$1,222.01	$1,222.05	$1,222.10