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	$159.30	3.866%	$165.4585	$165.46	$165.45	$165.50
Purchase #2	$55.33	13.665%	$62.8908	$62.89	$62.90	$62.90
Purchase #3	$54.27	4.867%	$56.9113	$56.91	$56.90	$56.90
Purchase #4	$244.69	7.591%	$263.2644	$263.26	$263.25	$263.30
Purchase #5	$82.91	3.503%	$85.8143	$85.81	$85.80	$85.80
Purchase #6	$222.87	6.260%	$236.8217	$236.82	$236.80	$236.80
Purchase #7	$55.65	3.481%	$57.5872	$57.59	$57.60	$57.60
7 purchase totals =	$875.02		$928.7482	$928.74	$928.70	$928.80