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	$250.43	3.774%	$259.8812	$259.88	$259.90	$259.90
Purchase #2	$84.39	5.189%	$88.769	$88.77	$88.75	$88.80
Purchase #3	$111.31	6.253%	$118.2702	$118.27	$118.25	$118.30
Purchase #4	$49.89	6.529%	$53.1473	$53.15	$53.15	$53.10
Purchase #5	$111.85	11.437%	$124.6423	$124.64	$124.65	$124.60
Purchase #6	$212.82	6.363%	$226.3617	$226.36	$226.35	$226.40
Purchase #7	$238.95	7.456%	$256.7661	$256.77	$256.75	$256.80
7 purchase totals =	$1,059.64		$1,127.8378	$1,127.84	$1,127.80	$1,127.90