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	$92.74	11.298%	$103.2178	$103.22	$103.20	$103.20
Purchase #2	$6.85	10.383%	$7.5612	$7.56	$7.55	$7.60
Purchase #3	$89.87	9.693%	$98.5811	$98.58	$98.60	$98.60
Purchase #4	$171.39	5.642%	$181.0598	$181.06	$181.05	$181.10
Purchase #5	$71.52	10.305%	$78.8901	$78.89	$78.90	$78.90
Purchase #6	$105.89	13.352%	$120.0284	$120.03	$120.05	$120.00
Purchase #7	$242.81	13.669%	$275.9997	$276.00	$276.00	$276.00
7 purchase totals =	$781.07		$865.3381	$865.34	$865.35	$865.40