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	$100.86	4.605%	$105.5046	$105.50	$105.50	$105.50
Purchase #2	$144.51	5.626%	$152.6401	$152.64	$152.65	$152.60
Purchase #3	$174.81	4.536%	$182.7394	$182.74	$182.75	$182.70
Purchase #4	$168.37	3.582%	$174.401	$174.40	$174.40	$174.40
Purchase #5	$96.69	4.839%	$101.3688	$101.37	$101.35	$101.40
Purchase #6	$172.57	6.188%	$183.2486	$183.25	$183.25	$183.20
Purchase #7	$49.96	9.203%	$54.5578	$54.56	$54.55	$54.60
7 purchase totals =	$907.77		$954.4603	$954.46	$954.45	$954.40