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	12.782%	$196.6354	$196.64	$196.65	$196.60
Purchase #2	$212.30	5.233%	$223.4097	$223.41	$223.40	$223.40
Purchase #3	$64.75	9.858%	$71.1331	$71.13	$71.15	$71.10
Purchase #4	$105.43	7.547%	$113.3868	$113.39	$113.40	$113.40
Purchase #5	$196.74	7.371%	$211.2417	$211.24	$211.25	$211.20
Purchase #6	$129.31	6.172%	$137.291	$137.29	$137.30	$137.30
Purchase #7	$234.45	6.835%	$250.4747	$250.47	$250.45	$250.50
7 purchase totals =	$1,117.33		$1,203.5724	$1,203.57	$1,203.60	$1,203.50