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	$102.73	11.427%	$114.469	$114.47	$114.45	$114.50
Purchase #2	$193.76	4.168%	$201.8359	$201.84	$201.85	$201.80
Purchase #3	$208.54	5.247%	$219.4821	$219.48	$219.50	$219.50
Purchase #4	$174.99	6.156%	$185.7624	$185.76	$185.75	$185.80
Purchase #5	$198.88	12.199%	$223.1414	$223.14	$223.15	$223.10
Purchase #6	$106.83	4.304%	$111.428	$111.43	$111.45	$111.40
Purchase #7	$32.65	12.783%	$36.8236	$36.82	$36.80	$36.80
7 purchase totals =	$1,018.38		$1,092.9424	$1,092.94	$1,092.95	$1,092.90