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	$217.28	5.557%	$229.3542	$229.35	$229.35	$229.40
Purchase #2	$201.61	11.663%	$225.1238	$225.12	$225.10	$225.10
Purchase #3	$92.71	10.107%	$102.0802	$102.08	$102.10	$102.10
Purchase #4	$82.93	10.106%	$91.3109	$91.31	$91.30	$91.30
Purchase #5	$115.68	10.522%	$127.8518	$127.85	$127.85	$127.90
Purchase #6	$157.43	6.348%	$167.4237	$167.42	$167.40	$167.40
Purchase #7	$29.28	11.476%	$32.6402	$32.64	$32.65	$32.60
7 purchase totals =	$896.92		$975.7848	$975.77	$975.75	$975.80