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	$125.77	13.119%	$142.2698	$142.27	$142.25	$142.30
Purchase #2	$161.33	12.577%	$181.6205	$181.62	$181.60	$181.60
Purchase #3	$190.68	3.190%	$196.7627	$196.76	$196.75	$196.80
Purchase #4	$27.85	12.158%	$31.236	$31.24	$31.25	$31.20
Purchase #5	$59.52	12.566%	$66.9993	$67.00	$67.00	$67.00
Purchase #6	$236.84	7.799%	$255.3112	$255.31	$255.30	$255.30
Purchase #7	$19.46	5.535%	$20.5371	$20.54	$20.55	$20.50
7 purchase totals =	$821.45		$894.7366	$894.74	$894.70	$894.70