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	$165.51	11.645%	$184.7836	$184.78	$184.80	$184.80
Purchase #2	$5.43	7.681%	$5.8471	$5.85	$5.85	$5.80
Purchase #3	$237.58	4.817%	$249.0242	$249.02	$249.00	$249.00
Purchase #4	$165.55	9.574%	$181.3998	$181.40	$181.40	$181.40
Purchase #5	$103.62	13.336%	$117.4388	$117.44	$117.45	$117.40
Purchase #6	$225.72	6.873%	$241.2337	$241.23	$241.25	$241.20
Purchase #7	$37.69	13.679%	$42.8456	$42.85	$42.85	$42.80
7 purchase totals =	$941.10		$1,022.5728	$1,022.57	$1,022.60	$1,022.40