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	$95.47	13.352%	$108.2172	$108.22	$108.20	$108.20
Purchase #2	$196.73	3.127%	$202.8817	$202.88	$202.90	$202.90
Purchase #3	$134.62	5.282%	$141.7306	$141.73	$141.75	$141.70
Purchase #4	$198.60	12.584%	$223.5918	$223.59	$223.60	$223.60
Purchase #5	$114.29	5.391%	$120.4514	$120.45	$120.45	$120.50
Purchase #6	$89.62	10.821%	$99.3178	$99.32	$99.30	$99.30
Purchase #7	$134.70	12.438%	$151.454	$151.45	$151.45	$151.50
7 purchase totals =	$964.03		$1,047.6445	$1,047.64	$1,047.65	$1,047.70