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	$152.44	8.512%	$165.4157	$165.42	$165.40	$165.40
Purchase #2	$81.34	5.544%	$85.8495	$85.85	$85.85	$85.80
Purchase #3	$40.56	4.747%	$42.4854	$42.49	$42.50	$42.50
Purchase #4	$78.80	3.541%	$81.5903	$81.59	$81.60	$81.60
Purchase #5	$224.63	4.369%	$234.4441	$234.44	$234.45	$234.40
Purchase #6	$225.29	12.508%	$253.4693	$253.47	$253.45	$253.50
Purchase #7	$228.86	7.435%	$245.8757	$245.88	$245.90	$245.90
7 purchase totals =	$1,031.92		$1,109.1300	$1,109.14	$1,109.15	$1,109.10