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	$55.82	9.335%	$61.0308	$61.03	$61.05	$61.00
Purchase #2	$176.82	12.179%	$198.3549	$198.35	$198.35	$198.40
Purchase #3	$30.43	4.506%	$31.8012	$31.80	$31.80	$31.80
Purchase #4	$213.76	13.742%	$243.1349	$243.13	$243.15	$243.10
Purchase #5	$174.73	4.286%	$182.2189	$182.22	$182.20	$182.20
Purchase #6	$180.91	5.242%	$190.3933	$190.39	$190.40	$190.40
Purchase #7	$161.42	9.373%	$176.5499	$176.55	$176.55	$176.50
7 purchase totals =	$993.89		$1,083.4839	$1,083.47	$1,083.50	$1,083.40