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	$177.57	10.555%	$196.3125	$196.31	$196.30	$196.30
Purchase #2	$137.70	10.721%	$152.4628	$152.46	$152.45	$152.50
Purchase #3	$63.85	5.700%	$67.4895	$67.49	$67.50	$67.50
Purchase #4	$228.28	4.139%	$237.7285	$237.73	$237.75	$237.70
Purchase #5	$149.43	11.406%	$166.474	$166.47	$166.45	$166.50
Purchase #6	$127.81	11.348%	$142.3139	$142.31	$142.30	$142.30
Purchase #7	$117.67	9.816%	$129.2205	$129.22	$129.20	$129.20
7 purchase totals =	$1,002.31		$1,092.0017	$1,091.99	$1,091.95	$1,092.00