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	$102.54	9.474%	$112.2546	$112.25	$112.25	$112.30
Purchase #2	$193.68	8.171%	$209.5056	$209.51	$209.50	$209.50
Purchase #3	$239.33	6.751%	$255.4872	$255.49	$255.50	$255.50
Purchase #4	$49.75	6.661%	$53.0638	$53.06	$53.05	$53.10
Purchase #5	$96.87	4.193%	$100.9318	$100.93	$100.95	$100.90
Purchase #6	$53.33	10.470%	$58.9137	$58.91	$58.90	$58.90
Purchase #7	$164.73	7.179%	$176.556	$176.56	$176.55	$176.60
7 purchase totals =	$900.23		$966.7127	$966.71	$966.70	$966.80