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	$142.55	11.280%	$158.6296	$158.63	$158.65	$158.60
Purchase #2	$40.98	4.712%	$42.911	$42.91	$42.90	$42.90
Purchase #3	$105.68	6.834%	$112.9022	$112.90	$112.90	$112.90
Purchase #4	$128.28	9.782%	$140.8283	$140.83	$140.85	$140.80
Purchase #5	$31.64	6.493%	$33.6944	$33.69	$33.70	$33.70
Purchase #6	$61.72	11.212%	$68.64	$68.64	$68.65	$68.60
Purchase #7	$67.32	8.385%	$72.9648	$72.96	$72.95	$73.00
7 purchase totals =	$578.17		$630.5703	$630.56	$630.60	$630.50