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	$237.82	12.225%	$266.8935	$266.89	$266.90	$266.90
Purchase #2	$72.74	13.357%	$82.4559	$82.46	$82.45	$82.50
Purchase #3	$145.74	4.836%	$152.788	$152.79	$152.80	$152.80
Purchase #4	$189.26	6.130%	$200.8616	$200.86	$200.85	$200.90
Purchase #5	$153.31	11.433%	$170.8379	$170.84	$170.85	$170.80
Purchase #6	$202.60	13.441%	$229.8315	$229.83	$229.85	$229.80
Purchase #7	$174.79	13.110%	$197.705	$197.71	$197.70	$197.70
7 purchase totals =	$1,176.26		$1,301.3734	$1,301.38	$1,301.40	$1,301.40