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	$97.83	3.745%	$101.4937	$101.49	$101.50	$101.50
Purchase #2	$62.77	10.682%	$69.4751	$69.48	$69.50	$69.50
Purchase #3	$250.45	4.738%	$262.3163	$262.32	$262.30	$262.30
Purchase #4	$50.84	6.810%	$54.3022	$54.30	$54.30	$54.30
Purchase #5	$75.89	7.427%	$81.5264	$81.53	$81.55	$81.50
Purchase #6	$45.78	12.443%	$51.4764	$51.48	$51.50	$51.50
Purchase #7	$73.66	6.143%	$78.1849	$78.18	$78.20	$78.20
7 purchase totals =	$657.22		$698.7750	$698.78	$698.85	$698.80