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	$101.89	6.276%	$108.2846	$108.28	$108.30	$108.30
Purchase #2	$156.76	4.849%	$164.3613	$164.36	$164.35	$164.40
Purchase #3	$187.37	3.305%	$193.5626	$193.56	$193.55	$193.60
Purchase #4	$242.98	10.868%	$269.3871	$269.39	$269.40	$269.40
Purchase #5	$104.55	9.373%	$114.3495	$114.35	$114.35	$114.30
Purchase #6	$112.56	3.474%	$116.4703	$116.47	$116.45	$116.50
Purchase #7	$99.52	10.399%	$109.8691	$109.87	$109.85	$109.90
7 purchase totals =	$1,005.63		$1,076.2845	$1,076.28	$1,076.25	$1,076.40