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	$148.41	6.146%	$157.5313	$157.53	$157.55	$157.50
Purchase #2	$26.98	7.504%	$29.0046	$29.00	$29.00	$29.00
Purchase #3	$223.98	4.257%	$233.5148	$233.51	$233.50	$233.50
Purchase #4	$19.25	10.480%	$21.2674	$21.27	$21.25	$21.30
Purchase #5	$115.65	10.212%	$127.4602	$127.46	$127.45	$127.50
Purchase #6	$212.76	4.334%	$221.981	$221.98	$222.00	$222.00
Purchase #7	$231.69	11.814%	$259.0619	$259.06	$259.05	$259.10
7 purchase totals =	$978.72		$1,049.8212	$1,049.81	$1,049.80	$1,049.90