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	$189.93	7.154%	$203.5176	$203.52	$203.50	$203.50
Purchase #2	$85.46	13.425%	$96.933	$96.93	$96.95	$96.90
Purchase #3	$136.90	4.368%	$142.8798	$142.88	$142.90	$142.90
Purchase #4	$55.41	7.736%	$59.6965	$59.70	$59.70	$59.70
Purchase #5	$148.80	4.768%	$155.8948	$155.89	$155.90	$155.90
Purchase #6	$134.68	4.658%	$140.9534	$140.95	$140.95	$141.00
Purchase #7	$157.29	10.838%	$174.3371	$174.34	$174.35	$174.30
7 purchase totals =	$908.47		$974.2122	$974.21	$974.25	$974.20