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	$38.92	13.695%	$44.2501	$44.25	$44.25	$44.30
Purchase #2	$150.27	13.500%	$170.5565	$170.56	$170.55	$170.60
Purchase #3	$71.64	7.227%	$76.8174	$76.82	$76.80	$76.80
Purchase #4	$52.75	13.408%	$59.8227	$59.82	$59.80	$59.80
Purchase #5	$185.76	13.598%	$211.0196	$211.02	$211.00	$211.00
Purchase #6	$241.65	3.845%	$250.9414	$250.94	$250.95	$250.90
Purchase #7	$181.80	9.260%	$198.6347	$198.63	$198.65	$198.60
7 purchase totals =	$922.79		$1,012.0424	$1,012.04	$1,012.00	$1,012.00