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	$139.45	5.595%	$147.2522	$147.25	$147.25	$147.30
Purchase #2	$202.77	3.212%	$209.283	$209.28	$209.30	$209.30
Purchase #3	$174.88	12.441%	$196.6368	$196.64	$196.65	$196.60
Purchase #4	$186.48	6.108%	$197.8702	$197.87	$197.85	$197.90
Purchase #5	$219.34	8.624%	$238.2559	$238.26	$238.25	$238.30
Purchase #6	$82.89	9.292%	$90.5921	$90.59	$90.60	$90.60
Purchase #7	$120.45	6.736%	$128.5635	$128.56	$128.55	$128.60
7 purchase totals =	$1,126.26		$1,208.4537	$1,208.45	$1,208.45	$1,208.60