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	$174.35	3.120%	$179.7897	$179.79	$179.80	$179.80
Purchase #2	$181.30	3.852%	$188.2837	$188.28	$188.30	$188.30
Purchase #3	$218.31	4.562%	$228.2693	$228.27	$228.25	$228.30
Purchase #4	$168.34	9.726%	$184.7127	$184.71	$184.70	$184.70
Purchase #5	$112.54	4.794%	$117.9352	$117.94	$117.95	$117.90
Purchase #6	$64.42	4.452%	$67.288	$67.29	$67.30	$67.30
Purchase #7	$113.29	5.451%	$119.4654	$119.47	$119.45	$119.50
7 purchase totals =	$1,032.55		$1,085.7440	$1,085.75	$1,085.75	$1,085.80