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	$70.61	9.863%	$77.5743	$77.57	$77.55	$77.60
Purchase #2	$234.94	11.229%	$261.3214	$261.32	$261.30	$261.30
Purchase #3	$31.74	12.591%	$35.7364	$35.74	$35.75	$35.70
Purchase #4	$29.81	8.453%	$32.3298	$32.33	$32.35	$32.30
Purchase #5	$86.30	4.800%	$90.4424	$90.44	$90.45	$90.40
Purchase #6	$94.53	6.121%	$100.3162	$100.32	$100.30	$100.30
Purchase #7	$202.65	3.187%	$209.1085	$209.11	$209.10	$209.10
7 purchase totals =	$750.58		$806.8290	$806.83	$806.80	$806.70