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	$196.65	6.435%	$209.3044	$209.30	$209.30	$209.30
Purchase #2	$246.73	4.712%	$258.3559	$258.36	$258.35	$258.40
Purchase #3	$131.81	5.576%	$139.1597	$139.16	$139.15	$139.20
Purchase #4	$199.60	5.422%	$210.4223	$210.42	$210.40	$210.40
Purchase #5	$228.75	3.133%	$235.9167	$235.92	$235.90	$235.90
Purchase #6	$105.34	11.504%	$117.4583	$117.46	$117.45	$117.50
Purchase #7	$82.88	3.676%	$85.9267	$85.93	$85.95	$85.90
7 purchase totals =	$1,191.76		$1,256.5440	$1,256.55	$1,256.50	$1,256.60