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	$247.31	6.302%	$262.8955	$262.90	$262.90	$262.90
Purchase #2	$174.53	5.194%	$183.5951	$183.60	$183.60	$183.60
Purchase #3	$94.35	3.392%	$97.5504	$97.55	$97.55	$97.60
Purchase #4	$59.55	5.606%	$62.8884	$62.89	$62.90	$62.90
Purchase #5	$195.41	8.393%	$211.8108	$211.81	$211.80	$211.80
Purchase #6	$51.65	4.514%	$53.9815	$53.98	$54.00	$54.00
Purchase #7	$242.40	11.330%	$269.8639	$269.86	$269.85	$269.90
7 purchase totals =	$1,065.20		$1,142.5856	$1,142.59	$1,142.60	$1,142.70