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	$221.32	7.796%	$238.5741	$238.57	$238.55	$238.60
Purchase #2	$91.41	9.255%	$99.87	$99.87	$99.85	$99.90
Purchase #3	$68.40	13.229%	$77.4486	$77.45	$77.45	$77.40
Purchase #4	$134.35	3.443%	$138.9757	$138.98	$139.00	$139.00
Purchase #5	$186.41	10.679%	$206.3167	$206.32	$206.30	$206.30
Purchase #6	$212.28	3.249%	$219.177	$219.18	$219.20	$219.20
Purchase #7	$59.56	13.372%	$67.5244	$67.52	$67.50	$67.50
7 purchase totals =	$973.73		$1,047.8865	$1,047.89	$1,047.85	$1,047.90