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	$127.53	11.163%	$141.7662	$141.77	$141.75	$141.80
Purchase #2	$182.89	8.576%	$198.5746	$198.57	$198.55	$198.60
Purchase #3	$187.76	6.663%	$200.2704	$200.27	$200.25	$200.30
Purchase #4	$209.67	12.262%	$235.3797	$235.38	$235.40	$235.40
Purchase #5	$68.29	13.826%	$77.7318	$77.73	$77.75	$77.70
Purchase #6	$237.87	5.245%	$250.3463	$250.35	$250.35	$250.30
Purchase #7	$77.75	5.270%	$81.8474	$81.85	$81.85	$81.80
7 purchase totals =	$1,091.76		$1,185.9164	$1,185.92	$1,185.90	$1,185.90