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	$42.90	6.379%	$45.6366	$45.64	$45.65	$45.60
Purchase #2	$15.83	10.530%	$17.4969	$17.50	$17.50	$17.50
Purchase #3	$106.41	5.133%	$111.872	$111.87	$111.85	$111.90
Purchase #4	$47.36	7.786%	$51.0474	$51.05	$51.05	$51.00
Purchase #5	$79.64	3.571%	$82.4839	$82.48	$82.50	$82.50
Purchase #6	$47.64	12.312%	$53.5054	$53.51	$53.50	$53.50
Purchase #7	$197.72	7.704%	$212.9523	$212.95	$212.95	$213.00
7 purchase totals =	$537.50		$574.9945	$575.00	$575.00	$575.00