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	$135.88	10.863%	$150.6406	$150.64	$150.65	$150.60
Purchase #2	$25.51	9.337%	$27.8919	$27.89	$27.90	$27.90
Purchase #3	$93.46	3.143%	$96.3974	$96.40	$96.40	$96.40
Purchase #4	$105.33	6.198%	$111.8584	$111.86	$111.85	$111.90
Purchase #5	$74.54	5.790%	$78.8559	$78.86	$78.85	$78.90
Purchase #6	$94.88	4.599%	$99.2435	$99.24	$99.25	$99.20
Purchase #7	$127.57	7.109%	$136.639	$136.64	$136.65	$136.60
7 purchase totals =	$657.17		$701.5267	$701.53	$701.55	$701.50