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	$146.79	3.760%	$152.3093	$152.31	$152.30	$152.30
Purchase #2	$111.88	9.349%	$122.3397	$122.34	$122.35	$122.30
Purchase #3	$78.48	8.314%	$85.0048	$85.00	$85.00	$85.00
Purchase #4	$133.59	13.696%	$151.8865	$151.89	$151.90	$151.90
Purchase #5	$249.37	5.238%	$262.432	$262.43	$262.45	$262.40
Purchase #6	$162.45	9.856%	$178.4611	$178.46	$178.45	$178.50
Purchase #7	$207.35	10.748%	$229.636	$229.64	$229.65	$229.60
7 purchase totals =	$1,089.91		$1,182.0694	$1,182.07	$1,182.10	$1,182.00