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	$217.96	5.731%	$230.4513	$230.45	$230.45	$230.50
Purchase #2	$89.34	10.197%	$98.45	$98.45	$98.45	$98.50
Purchase #3	$50.40	7.727%	$54.2944	$54.29	$54.30	$54.30
Purchase #4	$69.49	11.273%	$77.3236	$77.32	$77.30	$77.30
Purchase #5	$237.37	13.522%	$269.4672	$269.47	$269.45	$269.50
Purchase #6	$165.27	9.726%	$181.3442	$181.34	$181.35	$181.30
Purchase #7	$99.76	12.644%	$112.3737	$112.37	$112.35	$112.40
7 purchase totals =	$929.59		$1,023.7044	$1,023.69	$1,023.65	$1,023.80