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	$76.31	9.702%	$83.7136	$83.71	$83.70	$83.70
Purchase #2	$245.49	10.582%	$271.4678	$271.47	$271.45	$271.50
Purchase #3	$96.69	5.147%	$101.6666	$101.67	$101.65	$101.70
Purchase #4	$84.56	13.145%	$95.6754	$95.68	$95.70	$95.70
Purchase #5	$238.86	4.861%	$250.471	$250.47	$250.45	$250.50
Purchase #6	$27.26	3.839%	$28.3065	$28.31	$28.30	$28.30
Purchase #7	$116.52	5.757%	$123.2281	$123.23	$123.25	$123.20
7 purchase totals =	$885.69		$954.5290	$954.54	$954.50	$954.60