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	$45.46	5.235%	$47.8398	$47.84	$47.85	$47.80
Purchase #2	$116.97	6.779%	$124.8994	$124.90	$124.90	$124.90
Purchase #3	$173.42	4.804%	$181.7511	$181.75	$181.75	$181.80
Purchase #4	$56.58	5.712%	$59.8118	$59.81	$59.80	$59.80
Purchase #5	$33.63	7.117%	$36.0234	$36.02	$36.00	$36.00
Purchase #6	$98.53	7.341%	$105.7631	$105.76	$105.75	$105.80
Purchase #7	$67.93	4.409%	$70.925	$70.93	$70.95	$70.90
7 purchase totals =	$592.52		$627.0136	$627.01	$627.00	$627.00