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	$77.27	3.340%	$79.8508	$79.85	$79.85	$79.90
Purchase #2	$214.44	4.603%	$224.3107	$224.31	$224.30	$224.30
Purchase #3	$91.61	8.647%	$99.5315	$99.53	$99.55	$99.50
Purchase #4	$215.71	10.490%	$238.338	$238.34	$238.35	$238.30
Purchase #5	$55.87	12.632%	$62.9275	$62.93	$62.95	$62.90
Purchase #6	$56.59	8.486%	$61.3922	$61.39	$61.40	$61.40
Purchase #7	$105.64	3.503%	$109.3406	$109.34	$109.35	$109.30
7 purchase totals =	$817.13		$875.6913	$875.69	$875.75	$875.60