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	$142.35	6.771%	$151.9885	$151.99	$152.00	$152.00
Purchase #2	$175.35	10.381%	$193.5531	$193.55	$193.55	$193.60
Purchase #3	$40.26	5.671%	$42.5431	$42.54	$42.55	$42.50
Purchase #4	$104.73	4.423%	$109.3622	$109.36	$109.35	$109.40
Purchase #5	$43.96	8.800%	$47.8285	$47.83	$47.85	$47.80
Purchase #6	$36.35	3.206%	$37.5154	$37.52	$37.50	$37.50
Purchase #7	$82.43	5.162%	$86.685	$86.69	$86.70	$86.70
7 purchase totals =	$625.43		$669.4758	$669.48	$669.50	$669.50