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	$102.32	5.862%	$108.318	$108.32	$108.30	$108.30
Purchase #2	$152.92	12.225%	$171.6145	$171.61	$171.60	$171.60
Purchase #3	$79.69	3.234%	$82.2672	$82.27	$82.25	$82.30
Purchase #4	$66.84	6.820%	$71.3985	$71.40	$71.40	$71.40
Purchase #5	$140.37	7.178%	$150.4458	$150.45	$150.45	$150.40
Purchase #6	$191.91	5.448%	$202.3653	$202.37	$202.35	$202.40
Purchase #7	$192.32	9.241%	$210.0923	$210.09	$210.10	$210.10
7 purchase totals =	$926.37		$996.5016	$996.51	$996.45	$996.50