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	$82.42	3.660%	$85.4366	$85.44	$85.45	$85.40
Purchase #2	$156.70	10.315%	$172.8636	$172.86	$172.85	$172.90
Purchase #3	$231.61	9.639%	$253.9349	$253.93	$253.95	$253.90
Purchase #4	$86.52	7.129%	$92.688	$92.69	$92.70	$92.70
Purchase #5	$167.35	9.385%	$183.0558	$183.06	$183.05	$183.10
Purchase #6	$77.74	3.871%	$80.7493	$80.75	$80.75	$80.70
Purchase #7	$221.92	8.392%	$240.5435	$240.54	$240.55	$240.50
7 purchase totals =	$1,024.26		$1,109.2717	$1,109.27	$1,109.30	$1,109.20