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	$94.64	6.315%	$100.6165	$100.62	$100.60	$100.60
Purchase #2	$168.93	5.714%	$178.5827	$178.58	$178.60	$178.60
Purchase #3	$194.37	10.797%	$215.3561	$215.36	$215.35	$215.40
Purchase #4	$91.96	5.761%	$97.2578	$97.26	$97.25	$97.30
Purchase #5	$226.86	10.793%	$251.345	$251.35	$251.35	$251.30
Purchase #6	$92.37	8.839%	$100.5346	$100.53	$100.55	$100.50
Purchase #7	$206.59	8.393%	$223.9291	$223.93	$223.95	$223.90
7 purchase totals =	$1,075.72		$1,167.6218	$1,167.63	$1,167.65	$1,167.60