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	$239.92	13.785%	$272.993	$272.99	$273.00	$273.00
Purchase #2	$97.71	4.147%	$101.762	$101.76	$101.75	$101.80
Purchase #3	$112.43	10.225%	$123.926	$123.93	$123.95	$123.90
Purchase #4	$223.26	4.720%	$233.7979	$233.80	$233.80	$233.80
Purchase #5	$95.54	3.636%	$99.0138	$99.01	$99.00	$99.00
Purchase #6	$156.46	6.323%	$166.353	$166.35	$166.35	$166.40
Purchase #7	$41.44	9.774%	$45.4903	$45.49	$45.50	$45.50
7 purchase totals =	$966.76		$1,043.3360	$1,043.33	$1,043.35	$1,043.40