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	$68.79	13.799%	$78.2823	$78.28	$78.30	$78.30
Purchase #2	$248.64	10.592%	$274.9759	$274.98	$275.00	$275.00
Purchase #3	$83.85	8.381%	$90.8775	$90.88	$90.90	$90.90
Purchase #4	$106.71	5.871%	$112.9749	$112.97	$112.95	$113.00
Purchase #5	$126.68	13.199%	$143.4005	$143.40	$143.40	$143.40
Purchase #6	$129.61	10.314%	$142.978	$142.98	$143.00	$143.00
Purchase #7	$185.40	13.386%	$210.2176	$210.22	$210.20	$210.20
7 purchase totals =	$949.68		$1,053.7067	$1,053.71	$1,053.75	$1,053.80