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	$101.37	4.360%	$105.7897	$105.79	$105.80	$105.80
Purchase #2	$234.67	6.478%	$249.8719	$249.87	$249.85	$249.90
Purchase #3	$226.85	9.498%	$248.3962	$248.40	$248.40	$248.40
Purchase #4	$163.53	3.630%	$169.4661	$169.47	$169.45	$169.50
Purchase #5	$117.42	5.229%	$123.5599	$123.56	$123.55	$123.60
Purchase #6	$242.66	13.581%	$275.6157	$275.62	$275.60	$275.60
Purchase #7	$174.87	12.332%	$196.435	$196.44	$196.45	$196.40
7 purchase totals =	$1,261.37		$1,369.1345	$1,369.15	$1,369.10	$1,369.20