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	$187.35	4.647%	$196.0562	$196.06	$196.05	$196.10
Purchase #2	$168.73	10.306%	$186.1193	$186.12	$186.10	$186.10
Purchase #3	$187.93	7.801%	$202.5904	$202.59	$202.60	$202.60
Purchase #4	$85.27	6.154%	$90.5175	$90.52	$90.50	$90.50
Purchase #5	$106.32	10.634%	$117.6261	$117.63	$117.65	$117.60
Purchase #6	$106.60	5.446%	$112.4054	$112.41	$112.40	$112.40
Purchase #7	$89.40	3.139%	$92.2063	$92.21	$92.20	$92.20
7 purchase totals =	$931.60		$997.5212	$997.54	$997.50	$997.50