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	$189.72	5.672%	$200.4809	$200.48	$200.50	$200.50
Purchase #2	$79.32	6.828%	$84.736	$84.74	$84.75	$84.70
Purchase #3	$238.47	7.109%	$255.4228	$255.42	$255.40	$255.40
Purchase #4	$210.45	6.699%	$224.548	$224.55	$224.55	$224.50
Purchase #5	$110.98	13.300%	$125.7403	$125.74	$125.75	$125.70
Purchase #6	$118.71	4.126%	$123.608	$123.61	$123.60	$123.60
Purchase #7	$76.86	12.342%	$86.3461	$86.35	$86.35	$86.30
7 purchase totals =	$1,024.51		$1,100.8821	$1,100.89	$1,100.90	$1,100.70