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	$221.46	4.863%	$232.2296	$232.23	$232.25	$232.20
Purchase #2	$169.31	5.221%	$178.1497	$178.15	$178.15	$178.10
Purchase #3	$107.55	6.445%	$114.4816	$114.48	$114.50	$114.50
Purchase #4	$129.30	9.734%	$141.8861	$141.89	$141.90	$141.90
Purchase #5	$198.66	12.640%	$223.7706	$223.77	$223.75	$223.80
Purchase #6	$113.48	8.754%	$123.414	$123.41	$123.40	$123.40
Purchase #7	$233.32	7.421%	$250.6347	$250.63	$250.65	$250.60
7 purchase totals =	$1,173.08		$1,264.5663	$1,264.56	$1,264.60	$1,264.50