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	$153.75	5.611%	$162.3769	$162.38	$162.40	$162.40
Purchase #2	$80.86	6.691%	$86.2703	$86.27	$86.25	$86.30
Purchase #3	$99.59	4.426%	$103.9979	$104.00	$104.00	$104.00
Purchase #4	$198.71	6.860%	$212.3415	$212.34	$212.35	$212.30
Purchase #5	$64.59	4.557%	$67.5334	$67.53	$67.55	$67.50
Purchase #6	$45.66	3.553%	$47.2823	$47.28	$47.30	$47.30
Purchase #7	$148.70	5.375%	$156.6926	$156.69	$156.70	$156.70
7 purchase totals =	$791.86		$836.4949	$836.49	$836.55	$836.50