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	$85.82	4.277%	$89.4905	$89.49	$89.50	$89.50
Purchase #2	$223.93	5.845%	$237.0187	$237.02	$237.00	$237.00
Purchase #3	$55.72	7.720%	$60.0216	$60.02	$60.00	$60.00
Purchase #4	$199.30	3.324%	$205.9247	$205.92	$205.90	$205.90
Purchase #5	$61.42	5.833%	$65.0026	$65.00	$65.00	$65.00
Purchase #6	$167.55	10.656%	$185.4041	$185.40	$185.40	$185.40
Purchase #7	$195.92	13.685%	$222.7317	$222.73	$222.75	$222.70
7 purchase totals =	$989.66		$1,065.5939	$1,065.58	$1,065.55	$1,065.50