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	$228.96	9.419%	$250.5257	$250.53	$250.55	$250.50
Purchase #2	$172.74	10.737%	$191.2871	$191.29	$191.30	$191.30
Purchase #3	$45.79	13.835%	$52.125	$52.13	$52.15	$52.10
Purchase #4	$169.40	4.421%	$176.8892	$176.89	$176.90	$176.90
Purchase #5	$69.45	3.831%	$72.1106	$72.11	$72.10	$72.10
Purchase #6	$192.27	13.254%	$217.7535	$217.75	$217.75	$217.80
Purchase #7	$208.41	7.175%	$223.3634	$223.36	$223.35	$223.40
7 purchase totals =	$1,087.02		$1,184.0545	$1,184.06	$1,184.10	$1,184.10