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	$211.71	5.697%	$223.7711	$223.77	$223.75	$223.80
Purchase #2	$114.59	9.518%	$125.4967	$125.50	$125.50	$125.50
Purchase #3	$243.46	10.856%	$269.89	$269.89	$269.90	$269.90
Purchase #4	$76.69	6.613%	$81.7615	$81.76	$81.75	$81.80
Purchase #5	$173.97	12.264%	$195.3057	$195.31	$195.30	$195.30
Purchase #6	$39.90	7.352%	$42.8334	$42.83	$42.85	$42.80
Purchase #7	$60.52	3.224%	$62.4712	$62.47	$62.45	$62.50
7 purchase totals =	$920.84		$1,001.5296	$1,001.53	$1,001.50	$1,001.60