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	$176.43	7.744%	$190.0927	$190.09	$190.10	$190.10
Purchase #2	$89.32	10.845%	$99.0068	$99.01	$99.00	$99.00
Purchase #3	$149.59	4.714%	$156.6417	$156.64	$156.65	$156.60
Purchase #4	$107.56	10.253%	$118.5881	$118.59	$118.60	$118.60
Purchase #5	$198.83	12.272%	$223.2304	$223.23	$223.25	$223.20
Purchase #6	$189.42	7.776%	$204.1493	$204.15	$204.15	$204.10
Purchase #7	$62.34	4.107%	$64.9003	$64.90	$64.90	$64.90
7 purchase totals =	$973.49		$1,056.6093	$1,056.61	$1,056.65	$1,056.50