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	$244.48	4.553%	$255.6112	$255.61	$255.60	$255.60
Purchase #2	$219.78	12.818%	$247.9514	$247.95	$247.95	$248.00
Purchase #3	$168.69	11.174%	$187.5394	$187.54	$187.55	$187.50
Purchase #4	$60.99	10.395%	$67.3299	$67.33	$67.35	$67.30
Purchase #5	$93.86	9.256%	$102.5477	$102.55	$102.55	$102.50
Purchase #6	$79.99	13.247%	$90.5863	$90.59	$90.60	$90.60
Purchase #7	$104.53	5.644%	$110.4297	$110.43	$110.45	$110.40
7 purchase totals =	$972.32		$1,061.9956	$1,062.00	$1,062.05	$1,061.90