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	$165.56	4.790%	$173.4903	$173.49	$173.50	$173.50
Purchase #2	$115.56	10.219%	$127.3691	$127.37	$127.35	$127.40
Purchase #3	$89.82	10.268%	$99.0427	$99.04	$99.05	$99.00
Purchase #4	$217.81	12.749%	$245.5786	$245.58	$245.60	$245.60
Purchase #5	$96.80	10.590%	$107.0511	$107.05	$107.05	$107.10
Purchase #6	$104.89	5.233%	$110.3789	$110.38	$110.40	$110.40
Purchase #7	$241.89	5.633%	$255.5157	$255.52	$255.50	$255.50
7 purchase totals =	$1,032.33		$1,118.4264	$1,118.43	$1,118.45	$1,118.50