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	$182.34	3.629%	$188.9571	$188.96	$188.95	$189.00
Purchase #2	$68.35	7.228%	$73.2903	$73.29	$73.30	$73.30
Purchase #3	$202.27	10.141%	$222.7822	$222.78	$222.80	$222.80
Purchase #4	$7.35	4.661%	$7.6926	$7.69	$7.70	$7.70
Purchase #5	$98.27	3.699%	$101.905	$101.91	$101.90	$101.90
Purchase #6	$234.61	8.740%	$255.1149	$255.11	$255.10	$255.10
Purchase #7	$59.62	13.451%	$67.6395	$67.64	$67.65	$67.60
7 purchase totals =	$852.81		$917.3816	$917.38	$917.40	$917.40